Hi, Hookie
Thanks for sharing your Hellcat with us. It's a great looking plane you have there. I am confused with your comment of "horizontal failure" as well. On my Hellcat I couldn't find anything weak on the horizontal stab. Perhaps you could eleborate a little more, like bigbird already mentioned.
Bigbird, try to get "Helmsman Spar Urethan". It is a "MinWax" product. It comes in gloss, semi gloss and satin sheens. Sold at Lowe's or Home Depot. If you don't like the "rattle" cans it also comes in small cans. This is what I am going to use on my Cat.