I just register and saw this post. Boat name, thus user name is not correct and is being fixed. But-
I'm a retired wooden boat builder and we still do boat work, including varnishing etc on boats for customers.
We used Bristol finish on our mast also. We are in south Texas and our sun is brutal. We had been using Z-spar 2015 and it held up better than anything else we tried, but not on the mast.
The Bristol has been on the mast now for just over a year and is still flawless. My wife was working in a bosun's chair up the mast last week and looked it over- looks as good as when we put it on. We are hopeful now that we can get two years from it before having to add a coat.
On the toe rails, we tried varnish, etc, but as was said by someone else, unless you do the bottom also, water WILL get under there and lift the edges- Doesn't matter what you use- that's a weakness.
My wife (Laura) does our brightwork and she finally gave up on the toe rails, wooded them and keeps them oiled. She's switching every thing else to Bristol now.