Surfboard thickness

Hey guys, I've been riding an 8ft soft top over past 18 months. I've progressed on it to advanced beginner. Over the last 2-3 months I've started riding a 9ft resin (nice buoyancy - 3.25in thick 23in wide) I've got to the stage where I prefer the 9ft as it paddles easier and rides nicely. I am managing to handle it better and better. I can ride down the line, bottom front turn, back turn is a little tougher but am learning to shuffle back a little to help there. However I don't like it in bigger surf - too awkward to manage.
So I took out a board I had bought on a whim last year. It's a minimal 7ft 8 but only 2.75in thick. Now I cant paddle this thing. It feels like a submarine, wallows side to side when I paddle, nose often goes under. I can't get any speed on this to catch the wave unless I leave it very late...and that gets tricky. Once I'm up which only happened a couple of times - no problem I can ride it well and it feels much more manouverable than the 9ft. But basically a long session of paddling with not much else.
My question is - if I can find a similar board up to 8ft but much thicker say 3 to 3.25, will that give me back enough float to solve my problem?
I've seen these high end resin/soft tops that have similar profile to hard boards. A friend said that for the same volume as a hard board they should be more bouyant.
Any advice guys?
PS I'm only 5'7 and 67kg
cheers
So I took out a board I had bought on a whim last year. It's a minimal 7ft 8 but only 2.75in thick. Now I cant paddle this thing. It feels like a submarine, wallows side to side when I paddle, nose often goes under. I can't get any speed on this to catch the wave unless I leave it very late...and that gets tricky. Once I'm up which only happened a couple of times - no problem I can ride it well and it feels much more manouverable than the 9ft. But basically a long session of paddling with not much else.
My question is - if I can find a similar board up to 8ft but much thicker say 3 to 3.25, will that give me back enough float to solve my problem?
I've seen these high end resin/soft tops that have similar profile to hard boards. A friend said that for the same volume as a hard board they should be more bouyant.
Any advice guys?
PS I'm only 5'7 and 67kg
cheers