I wouldn't go as high as 40lb in a kayak, and definitely wouldn't go much higher than 20 in a float tube. The beauty of kayak fishing is the fish tows you through the water so you can use lighter gear. I wouldn't want to be pinned to a 70lb seabass boatside with 25lbs of drag and 40lb line that decides to make another last ditch dive. Big potential for flipping there...

My general La Jolla rod set ups are:

20lb plastic- 400S/Rainshadow 967
25lb bait- Progear 545/Calstar 700ML
30lb surface iron- narrow Penn 500/Calstar 800L
30lb heavy iron- TLD 15/30/Sabre Stroker

Your main concern should be getting spooled, because from a kayak, or float tube especially, you really don't have the leverage of a solid platform to put the screws on your drag. It's also dangerous, like I said. It's a good idea to back up your smaller setups with spectra, something I haven't gotten around to doing yet.

If you're gonna do a lot of casting lighter baits like plastic, then something like a calcutta 400 with spectra backing, or even a small trinidad would be good. For iron and bait you can get by with just about anything, from old Penns to Accurates. Depends on what you'll be using the reel for.
-Brian