Hey!
I have a Vader too, and let me tell ya' Vader is ridiculously hot even with fans and the weight is just nuts. Compared to Fett, I'll wear my Fett any day, other than the fact that I simply love the costume but the comfort is FAR better.
I was hit by a drunk driver in 2006, have several herniated discks in my neck and back, alot of permanent pain, and the Fett feels SO much better than Vader. I could wear Fett, comfortibly for A LONG time and not have an issue, whereas with Vader, 2 hours and I'm starting to hurt. lol On Halloween this year, I wore my Fett - with a non-supportive jetpack harness - for over 6 hours straight and the only thing that gave me a bit of an issue was the harness on my shoulders. But that's fixed now that I have a 100% accurate steel jetpack harness from BFUK and MojoFett, AND I have another backup harness form FettDad which is set up the same way, with support all around as opposed to just having the pack hang off your shoulders. I'll be able to troop in it pretty much as long as I feel like it and my only issue will be when I have to use the bathroom. LOL
As far as the topic, I went for as dead on accuracy as possible, and then when I worked the outfit to fit me, I worked it to be as comfortible as possible without sacrificing accuracy and it works fantastic!
Good luck!
J