Mike,

The reason you are getting the seam showing is the balsa is not stabilized being just two pieces of wood glued on edge. That being said, I have had it show up just a hair on a finished plane as well. I think it is due to the silkspan underlayment being so thin, something may telegraph through.

The way to minimize it its to let the Minwax dry (cure) before you shoot the primer. Keep in mind we are dealing with a water base product and it takes time for all the water to exit the finish. What is happening is the primer can lock in the water and the MinWax continues to shrink telegraphing what is below it. What I do is bring the wings and stabs into the house if it's cold in the shop for a couple of days to let it dry before priming.

A little telegraphing is just telling us we have an extremely thin finish, but you can reduce the chance.

No suggestions on paint. You are running up against compatibility. That's why I stick with Klass Kote epoxy primer as I know you can shoot just about anything over it and it will stick. If you stick to Matt and my methods you won't have a lifting problem at all. You should be fine with just about any brand of good quality top coat over the Klass Kote primer. Even good quality water base auto paint should be fine.I know what works for me, so I just stick with it.

I like the blue 3M and haven't had a problem with it. I have been using the green stuff for a few years and just like working with it. The key to getting a clean edge with the green 3M is to always clean the edge with a good cleaner like the stuff Coast Airbrush sells. The Coast cleaner is exceptional.

One other thing, I can't bring myself to use regular tan 1/2 or 3/4 inch masking tape on fresh paint. To me it just sticks too good. I get some leaking with the low tack blue, but I have never had it lift paint, so I stick to it.

This stuff is like anything else....it's a system...and if you experiment it may come back to bite you.