Okay, I'm getting serious about ordering a couple of bikes. The RadRover for me and probably the RadCity for the wife. I'm not sure of which size to get for her, the 16 or the 20. She's about 5'7" tall and that calls for the 16 on the website. However, I may end up using the bike once in a while and I'm 6'0" which calls for the 20. Is there that much of a difference? Would she be okay on the 20? Neither one of us have ridden bikes for years and we're hoping the electric bikes will help get us back into riding again but I don't want to end up with a bike she won't use.