I'm 6'2" pushing 6'3" and use a GA 88/4500 as my main tank on my axe. I posted this picture in the ninja 90 SL tank thread to show the length.
The GA 88 seems to measure an inch more than what is listed (11.2" with reg), unless I was meant to measure from the base of the threads and not the top. This actually puts the 88 as almost the same length as the new ninja 90SL(12.25"). Obviously there is a difference in price but the 90 would give even more air.
As far as comfort. I personally like the 88 as my setup. I don't feel like restricts my movement except superman diving/sliding because it's a big tank to tuck into diving position if that makes sense. That doesn't really matter though since I rarely dive that way. For a back player who is tall I think it's a great tank. But I'm obviously bias.