looking for seat bottom suggestions...

duct tape

Bingo!

Here's what I ended up doing. It still needs some refinements, but it should at least be usable in this form.

Nice! Is that your original seat bottom?  I've got an older Perception that I might do something similar with.  If I can keep my butt dry and comfy for a longer time, that one will probably end up being my crabbing setup.  It's got a long more space for crab rings/traps than my pedal kayak.

Did you use 3/4" PVC, or larger?  Not sure 3/4" PVC would hold me for long, I am about 220lbs. 

Seems like a dream to sit on compared to the vantage seat

Did you use 3/4" PVC, or larger?  Not sure 3/4" PVC would hold me for long, I am about 220lbs.

Yes, I used 3/4", but I only weigh about 150. I bet that 1" would be sufficient.

I tried out the seat today, and I love the design--very, very comfy. There are a couple of issues, though (seat is slightly too narrow, the connection between bottom and back was not quite right, and the seat was a bit too low in front), so I'm going to try to make a new-and-improved version over the next couple of days, then test it out on Saturday...