Here is a quick update on the epoxy front.
I sent emails to Precision Epoxy and one other place to get quotes. No response. After three days, I called Precision. I nice guy called me back, and said they had been busy. We talked for a while and he said he would quote a kit with everything I need. I'm a bit afraid of what the price will be. I'm also worried that my little sale is too small for them. We will see. I'm still waiting.
Here is a few things I learned from the Precision Epoxy guy:
1. The FP-90 epoxy is their "Aerospace Test Bed" product. It makes an extremely flat surface, but he said it isn't intended to be touched! It isn't that strong. He said I don't want it. He recommends the FP-85 product.
2. This is the important thing he said: A self-leveling epoxy layer should be a minimum of 1/4 inch deep, with an absolute minimum of 3/16.
3. To self-level my 5 foot rails, he recommends three bridges between them: two end ones 6 inches from the ends, and one in the middle.
4. The bridges should be the same width as the rails, so if the rails are 3" wide, the bridges should also be that wide. That way everything is the same and it will level well.
5. He said that he has had people pour self-leveled rails that are 25 feet long!
I will give Precision a few more days, then I'll start talking to other suppliers.