Rick,
Measure the distance between the top of the mast and the attachment point for the shrouds, divide by 3, dont go any higher than that distance above the shrouds attachment point and you should be ok with the spin.

HOUNDS, the place next under the head of a mast, where it is made more substantial for supporting the trestle-trees and top. (I probably wasnt using the term right, sorry about that)

How much uni? I dont really know, I'd start with one layer of 4oz and see how stiff the rig is. Hang 20lbs off the tip of the mast, and measure the deflection, then do it again when after you add the uni and post the results. The sail is going to act as a backstay, so as keep the sail tight it will help support the mast.

Clear coat, Imron is the best and gives the best finish when sprayed professionally. If you want to do it in your basement and dont want to kill yourself with the fumes, System Three WRU works good, but only lasts a couple of years and it does flake off over time if you scratch it, I but it works for a while, not nearly as long or as shiny as Imron. System Three is waterbased and the fumes are low tox, so its easy to work with in your house. If you spray Imron or any of the 2 part marine paints, you need to have a respirator, if you breath it it can kill you.

You might want to wait until you test out the mast before you sail it, you can always add more uni, or sand some off to tune the rig.

Bill