Yes it does help IMO. Absofrickinlutely. And I am pretty sure EJ thinks so too, which is why they made and sell the sweet cheeks seat pad. Its a vacuum mattress seatpad with beads in it (100% fill or 200% fill ) that you conform by sitting in it and then suck the air out so it stays in the shape of your keister.
I use the 200 in my 4fun and have had really great results, and its comfortable, and it locks your legs in a little better to the thighbraces. I use the 100 in my Superhero with happy results too.
It comes with the elite JK boats. neither of mine are. I bought one for the SH because I missed it paddling the first run or so without stealing the one from my playboat.
for reference, I am @ 5'7, 235lbs (short and stout) paddled a Wavesport EZG (for 5 years and ate a lot of shit thinking I was a crappy boater) and last year I bought a used Karnali, without demoing it, and I swam three times, the first day i tried it, because it was huge on me- like a supertanker. I seemed to flip over and just stay that way. when I traded it in, (on a villain :]) the pyrhana rep tried to convince me to try it again with a seat pad. I politely declined, having developed a serious aversion to that POS boat.
I hopped in several different JK boats and have had great success since. It may be that I was out of shape (I was), or that the EZG and karnali werent great fits for me(they weren't) but I have lost some weight, and been paddling hard. (i have swam this year, but it has been on class IV, and when i get tired and sloppy) sitting higher in the boat has a lot to do with it, along with rest of the package, but either way I have been feeling much better in my boats. everything fits better in a JK boat. ( same reason some people cant stand em. different fits for different folks). I traded in the villain on a 2011 superhero, because it has a smaller bow, and fits me better for my low water manky stuff I do trying to get better at creeking.
Hope this helps.