it sets evenly, the only watch out will be on the areas around the body mounts, it definitely added extra material which made it difficult to clip the body pins to the body mounts. i had to cut around it afterwards (the holes on the body).
I just did this to my NERO body. Started with shoo-goo with dry-wall tape. Waited it to dry one day. Then I put down a layer of Leak Seal (Krylon brand rubber coating). I feel the strength came from the shoo-goo and the dry-wall tape. Other than the added weight of the rubber coating I can't really say it made it any stronger. If there was a good way of thinning down the shoo-goo that would be perfect in my opinion. Maybe getting a solvent that I could brush over the shoe-goo so it spreads more evenly and in thinner layers.
I coated mine as well. But just a hint. Flex seal while decent, I don't find does as good a job as Rustoleum. I guess its really just preference. But the flex seal can be a bit spatchy. The Rustoleum Bed Liner works great and doesn't add a ton of weight like the Flex Seal and tape.
As you can see the Rustoleum Bed Liner looks much better. And it follow the outlines of the truck body much better. This limits the clumpy like feeling of the Flex Seal. It also only cost roughly 7-9 dolars a can and is enough to do multiple bodies. I did two coats on this application and I love it. I am not saying that the flex seal won't work just that in my experience this does better.