Hi Garry
I'm fairly sure that "Okoume" and "Gaboon" are used interchangeably for the same stuff.
I undestand that China is shipping a lot of cheap Okoume ply these days, so that might be the $28 stuff you've seen. I've heard that it's not as good quality as the stuff coming from Norht Africa, Israel etc (which is probably the $59 stuff. Eiteher is probably fine for your job, But I would personnaaal not take the risk with Chinese stuff I hadn't inspected before purchase.) . I used Israeli stuff and it was/is perfectly fine.
The really best stuff comes from Europe. Denman Mariine sells Joubert brand (French stuff) for $79 for 4mm and $120 for 6mm. It is subbosed to be very high quality construction and best quality woods used.
If you want floating furniture, with the best possible brightwork, I'd spend the extra few bucks for the Joubert. Otherwise, any decent Okoume/Gaboon will do the trick, and the results will still be very impressive.
I don't know about pacific maple, sorry. I can't imagine it being better than Okoume, though.
Not sure if you've done any boat wood work before. If not, here's a few tips I learned the hard way:
The four things I'd never be without are my Japanese pull saw, shinto rasp, low-angle block plane and my hand (ie not electric) drill (for doing the billions of stitch holes). I really hate power tools due to the mess and noise, and Okoume is so easy to work, you don't need them 95% of the time...
Always keep your plane blade razor sharp. If you haven't used one before, you-tube to learn proper technique for using and tuning the plane. Makes a huuuuge difference to speed, ease, and accuracy.
I went nuts trying to fine the right gauge copper wire at anything approaching a reasonable price in Australia. Then, I discovered ordinary yellow-and-green 7-strand earthing cable at the local electrical/lighting supplys place. Like a buck a metre or something, and one metre yields 7 metres of perfectly sized wire. Easy to strip the cover off too. Just be sure to get the 7-strand not the type with dozens of tiny strands.
Measure forty times, cut once!