RE: Top Flite 1/7 P-51 Build
Bob's idea on the lower cowl mod sounds like a reasonable short cut. You might just tack glue some soft balsa blocks there for the entire lower cowl, shape it to your documentation, remove it when done and use it for your plug (saves buying a cowl and modifying it). Just repeat that process for your radiator belly scoop plug. You might save time with Bob's idea.
No, I don't have that book. I do think the book we do both have is usable, and good.