Corossion
Darrell,
I noticed you live in Houston. I'm also in Houston and building a 7. I am using the Sherwin-Williams 3 part epoxy and have used the SW wash primer that Vans recomends with decent results on several surfaces. I switched to the epoxy because it's overall application prior to topcoat is easier.
I don't have to tell you that in a coastal climate like we're in priming is highly recomended. I once had a Cessna that I sold in Houston. The poor guy let it set out for several years and it was a total loss at annual due to corrosion.
Like Pete said it all comes down to how your going to store and maintain your plane and an overall personal choice. It does drive up the cost though. A good alternative is a product called ACF-50. It's a MIL spec product used for controlling corrosion on aircraft electrical, avionics systems and airframes. It dries like a wax inside the wings and fuselage and is usually applied after the plane is painted. I have an A&P friend that only uses this stuff and he loves it.
Good luck with your project. I would be happy to show you the primer products and pass along some names and numbers of SW reps that can help in Houston.