I noticed that with my M66. I actually wore my belt tighter than I had to with a fullsize 1911 IWB, seems like iwb doesn't need to be quite as tight to stay in place just as well. I ended up loosening my belt one notch and letting the holster droop just a bit (much like in Chris' Defender pic), it's only going so far and, for some reason, my legs feel better when they're able to get blood flow

. I see several Def-Cons in my future now, just need to decide which gun to start with.
As far as the Sparks' ExC, I'm not familiar with that particular model but Tony and the guys do first rate work. I'd think the flange concept would be similar in effect to Gary's Max-Con V - avoiding pressure on the sciatic nerve.
I've owned Sparks leather in the past (Watch Six, D-4C and belt) and was well pleased with its quality and construction. Brommeland's designs suit my needs better and I find the gear a bit more comfortable to wear. Could be my build or the way I carry but that's why having choices is so great.
Find the maker that suits your needs and you're set for years! Sparks, Brommeland, K&D, Garrity, Del Fatti, Alessi, HBE ... it's a good time to be in the market for leather :yup:.