The neck angle is fixed at 38 degrees, which was higher than I thought I wanted, but works very well for me, and I now know that I wouldn't want it any lower for the road. I am also 5'4", with a slightly shorter X-seam and the trike fits my dimensions well, but I'm a bit longer in the back than you.

I haven't been on the trike long enough to tell what the long-term comfort factor is. I'm just getting over two badly fracturesd ankles and don't have any cartilage in the right one, so I can understand what it's like to have to work from a weakened state. I am having trouble getting up to speed--no pun intended. That makes me very slow, period, because I'm not even up to full walking strength. Fortunately, I have a great low gear, around 13" I believe. I'm not that competent with gearing, but I believe my dealer substituted a 54-42-24 cassette for the stock one to get this. I can crawl up a hill pretty well with my low gears, but just don't have the stamina yet to do much of that. If it were much heavier I would dispair, but the trike is light and nimble and I know it will be a gas when I get my legs back. By the way, I also have serious neck issues, which is why I have a trike in the first place. No problems yet with that and maybe never.
Hope this helps. Write me directly if you prefer.
Regards,
Carla
shamusky@earthlink.net