Did you swap out the layshaft bearing? I realize that doesn't answer your question, but if you haven't then the end play now is moot. You would want to take care of the bearing and then worry about the end play. I didn't have a dial when I did mine. I knew from the bearing type I installed that shimming was likely so I had a number of them on hand. It was a bit of a slow process but I added them until I could feel a slight pressure on the kick start lever when I turned it over and then removed .005. Not very scientific but the result was that my end play was very slight when cold (barely perceptible), and so assume a bit more when warmed up. The gearbox has been happy ever since. I do not know at what number you go from OK to not. I just know that less is better so long as it has some.
Russ
PS-I think the sealer is not going to be an issue and it could be argued not to use any at all. Heck, just torque it down a couple extra pounds and you will probably be at .008!