I've no experience of Owatrol, but if it dries solid I wonder what happens if it gets chipped. Get moisture get under it? Like the usual underseal. No doubt someone will be able to answer that question.
I'd go for Wax-oil as it spreads into nooks and crannies.
I can only get just over five with mine. With those narrow rear tyres I got off you, the rear end has gone up an inch. I need to raise the front end to compensate.
I like it and the way you've made the top bar. I can see a nice little earner there.
BTW. Where did the caution sign come from? Very apt.
Just one observation. I'd fit gussets in the corners of the top bar. Add a bit of strength.