I've used the 'Happy Bottom' (aka Creature Comfort) seat and it was OK

I was mistaken on that.
My apology.
I thought CLC had just renamed the 'Happy Bottom' seat.
I've never used a Creature Comfort seat; I don't think it would suit my paddling style.
http://www.clcboats.com/shop/products/boat-gear/creature-comfort-seat.html

This is the HappyBottom seat:
http://www.clcboats.com/shop/products/boat-gear/kayak-seats-foam/happy-bottom-pad-kayak-seat.html

Whatever seat you choose, if you want the boat to feel more tippy, use a thick seat or mount the seat with a good space under it! :-)
It amazed me when I found a marked difference in 'feel' with 1/2" of seat height difference.
For surfski training, some paddlers use a seat pad to reduce the boat stability and then remove the pad on race day.