I agree that going back to thick rails is a non starter.
My buddy had an old 9'2 that I used to love, so we swapped in the line-up for a few waves.
So corky, I could hardly even stand on it.... when I tried to throw a turn, it felt like a barge.
BUT.... thickness and volume don't have to equal thick rails.
My GenRation Wedge is 9'2 x 32' at 167 liters------ 5 5/8" thick

But by using "S" rails, there is plenty of volume in the deck, but the rails are low performance rails (pic)
I get lots of comfortable volume in a board that will lay down a harder and crisper turn than I could ever throw.
It's more about design than mere numbers.
These boards were designed to win on the world tour, by guys who want to float at their ankles... while all the competition is sunk to their waist.
It's the board I used on the biggest day in my recent "5 Days" video.
Totally awesome..... and thick

But it should be ridden at the smallest you can manage, or it will be corky.
My 9'5 was too much volume for me.
The 9'2 is fine for me, but I could go smaller.