We recently bought a double kayak and had the same kind of issues as you, in the end we went for a plastic one, pros for us were:
– We use it in rocky Cornish seaside areas
– Seating position seems far better (proper footrests etc)
– Our local lake has a no inflatables policy
– Rigidity
Cons of course:
– Storage! A double kayak is huge
– It’s heavy, getting it onto the roof rack is a two person job, also make sure you get a trolley for getting it to the beach.
Recently did a 480 mile round trip to Cornwall and didn’t notice any difference in fuel economy with it upside down on the roof, overall very glad we bought a plastic one, but it is a bit of a pain to store and move around.
Bought ours from Galaxy Kayaks, they had a deal on when we got it so all in was under £400.