I was riding with a20.25 frame, it'll be ok 

I think for most things, 20 or even 20.5 should be fine.  The only time it would an issue would be that you'll have to get used to a higher jump to do decades (which most riders don't do anymore) and depending on how long your legs are deathtrucks might be a problem (again, not many people do them). 


On the other hand a long BACK end of the bike makes a flatland bike feel super sluggish, but in the last 5-10 years most ramp bikes are as short or shorter than a lot of flatland bikes were in the 90's/early 2000s, so anything modern should work fine.  I would think something like a 20.5 Sunday Funday would work great for flatland.   


I liked the big bikes for some stuff, there's lots more room to move up front and it doesn't feel as cramped.  Since our bikes essentially descended from tiny 18.5" top tube bikes made for middle schoolers, sometimes I wonder if the super short bikes are more just because that's what we've always used.  [size=78%]     [/size]

I think you will find it a little bit long for spinning stuffs.

I tried a 20.5 and didn't like it.
Yes it felt roomier, but I found to my surprise that a smaller sized frame but with a 14" rear was a lot better.


And you know its true.
Anyone who likes big butts can not lie.

20" is about enough. no more for Flat only.

And you know its true.
Anyone who likes big butts can not lie.
 
 
This shop I am looking at this bike is in a rough neighbourhood, all their bikes do not have pedals attached and when I asked if I could test ride the bike they said "We don't normally do that". Understand if it is raining although that is a little silly, if I go back a second time they might let me ride it!

I ride 20.3TT and im 5'8. feels alright.