Do be aware if you test ride that the stock stems on the terrys are quite short. I had to put longer stems on all my terry, but that only improved the handling. I agree that the 50 is probably too big if you had problems standing over it and seat was too high in the lowest position. I'm also not sure I would trust this LBS, he may have just been trying to 'fit' you with what he was trying to unload........ The 17.5 could be spot on for you.