I'm with Stan on this one, catching and releasing a nesting Tuc is fine as long as you target just one, release gently, and move on. Spawning time is best time to hook into a sizable Tuc with any regularity in my experience. Your flies look fine, beside they have to look like weak vulnerable prey to get strikes.
As far as kayak stability you might consider what I did for my 11' canoe which used to be quite squirrelly, I made a lightweight removable outrigger setup using PVC pipe for the iako, and either 2 lobster trap floats, or a cheap ($3.99) "pool noodle" for the ama.
http://www.hawaiibassfishing.com/forum/ ... ight=#2344
I can stand and cast all day without suffering from huli-ova-fobia.

I've tested my outriggers in rough seas 3 miles out in Kailua Bay with flying colors. Here's a couple pics:
Pool Noodle Ama
Lobster Float Ama
