I've been wearing a size 7 Pro Force for about a year. I'm 6'4" 220 lbs right now, and it's too loose. It fit me perfectly when I got it, but I was 250 lbs then. When I lose about 10 more lbs I'm going to spring for a more expensive uniform, probably a Tokaido, which most of the instructors and advanced students in my club wear.
You are definitely heavier than most practitioners of your height. I think that getting a larger gi altered is your best option in the short term. Down the road you may think about dropping some weight... it will improve your training no matter your art, and it's something you can think about and focus on even when you aren't in the dojo.