I know what you mean, I have a gel seat which has a rip init and took to of to send it back, so I put the original back on.
I went for a ride 160 miles my usual route and my ass, you put it perfectly.
I thought it was that bad that I put the gel seat back on, I will wait winter.
I tryed to find out why it was so bad, the seat seems to have plenty of padding, quite nice I thought for a modern bike,
so I thought it might be the heat so I went for a ride and when I came to a stop I put my finger under my bum where it gets sore but there was no heat there, not the most scientific but I don't think it's heat, well not burring hot.
I know it was the same when I bought the bike thats why I bought the seat and know it has a cat free pipe it's the same,
The pipes are just as hot or near as I can tell, might be a little bit cooler but not the amount you want.
ps dont you mean boil on the bag