I did the open bays on my Avanti this way. I did a 3 coats of Nitrate on any raw wood, and 1 coat only on the open bays where I had SLC, then put silkspan over it the usual way.
The usual way - > Cut silkspan for the bays to size, sprayed with water from old Windex bottle, lay it on the plane, (bottom panels first) brushed down edges with some really thinned Nitrate (like 3 to 1) let it dry and pull tight, then put on one wet coat of dope over everything, then 1 coat with some of Randy's Aero Zinc filler, sanded smooth, and one final thin coat of dope. Ready for primer. Worked great.
Open bays are darn near bullet proof with the SLC under the silkspan!
EricV