Pinarello Paris size advice

Does anyone here have experience with the Paris normal and/or easyfit frames? My daughter needs a new frame, she currently has a Specialized Sequoia (aluminium) size 49 (TT 51.8) that she has had since she was 12 - she is 18 now. Last year she started having lower back problems and we took her for a bike fit, they adjusted a few things including changing thestem for a longer one (110) but said that basically the frame is too small for her and they could not get a perfect fit. We have been looking to upgrade her bike and get a new bike or frame (her bike now has ultegra components and wheels), but we live in South America and there is very little choice available. For example last year there were a few amiras and treks, but all were too small. We could now get a ruby sport in size 51 but the components are not as good as the ones she has....and I think she is after something a bit racier... The other day she saw (and fell in love with) a Pinarello Paris easyfit frame, the cost is about the same as the ruby complete bike, but the shop assistant thought it would be too big for her - it size 51 with TT 54.5. He said he had another Paris bike (NOT easyfit) in another shop in size 50 and on paper the size did seem to be better - TT is 52.5. It was also a 2012 model and less expensive! However when she tried it it did not seem right somehow - the height was OK but she has a long femur and the setback did not seem enough, her knee was way past the pedal center and the seat was already quite far back. So now we wonder whether the 51 easyfit would infact be better.....she is 166.5cm (nearly 5 foot 6) but has inseam 80.5cm (31.7 inches). The length of her arms stretched out finger tip to finger tip is the same as her height. Problem is that the easyfit its just a frame so its difficult to try unless we leave her bike and change over all of the components which they kind of reluctantly offered to do, so if we do this I feel we're almost committed....

I should add that she also sometimes rides my husband´s Roubaix which is size 52 (TT 53.7 with 90 stem) and she likes this a lot better than her bike, at least on longer, flattish rides, I think she prefers hers for climbing. On her bike she is quite upright and it hurts her back more, on the roubaix she is more stretched out, her back is more comfortable though she does have a bit more strain on her wrists and forearms, however its not really set up for her. The reach on the roubaix is given as 379mm, on the Paris easyfit 51 it is 375 and on the Paris 50 it is 372......the ruby 51 is 370......

She trains for inline speed skating (maybe back problems from this rather than bike?), the cycling is part of the training, they usually ride from 4-6 days a week, alternating between "flat" (40-80km generally) and clmbs (12-20km), she is quite strong. She ocasionally takes part in road bike races too.

Sorry this is long but thought I should explain the situation as much as possible. I would be grateful for any advice or feedback.

Thank you very much for your helpful reply - I have read the other posts (will probably read again later as some of that is quite complicated, but I get the main points..). Yes, I am sure your bike #2 is the Paris 50 we are looking at. In fact we might go and look at this again and see if we can adjust the saddle position at all, as theoretically the size should be in the right ball park. Also we can try a shorter stem as this bike was already made up and had a 120mm stem. Last time we were pushed for time, I thik we need more time and a test ride if they will allow....... I think the bike #4 is too small as its smaller than her current bike, though I know the different geometry could affect things. And I think unfortunately that the beautiful 2013 easyfit 51 they have will be too big (the 49 probably would have been just right but not available....). Initially we were thinking that it might not be too big as she does ride the Roubaix with a top tube that is just 8mm shorter, but the roubaix has a 90mm stem and I am sure this would be the shortest feasible on a Paris. The Roubaix has not been set up for her but she does feel some pressure on her wrists and forearms which may suggest its slightly long? But her back is much better on this bike than on hers and this is the main issue we want to resovle (as well as getting a better bike)......My husband is only slightly taller than her, his legs are the same length but his torso longer and shoulders broader. I dont think her arms are particularly short or long, her arm span is exactly the same as her height, but obviously her shoulders are narrower than most men.

How do you find the Quattro? We would have considered this, but the only one they have is definitely too small.....I dont think there have been any major changes in the frame since 2012 (except now its think2 but there are not any 2014 ones here anyway....) so it shouldnt matter that we are looking at a 2012 model?

Once again many thanks for your help.....

Thanks so much for all your advice. It's actually very difficult to get bikes here because of customs restrictions, it takes ages! The Specialized shop we usually deal with still have not got the 2014 bikes that were supposed to arrive last November, then January, then February....to order specially will take a long long time and cost more...

Anyway we went back yesterday, spent more time there and I think after all the 50 frame will be fine. We were able to move the seat back more than we initially though, and the reach is not too much even with the 120 stem. As it's a 2012 it will cost us quite a bit less (under 3k) which is advantage too. Actually its very lucky they are willing to sell just the frame as this is a complete bike really and it's very hard here just to get a frame........shame it looks so nice with all the matching components but we can't afford the whole thing!

By the way her crank size is 170, I think this is correct for her.

Anyway, once again many thanks - we should be getting the bike next week.....