I wasn't happy with the canopy I had, so I came home from Michael's with a new option, in the form of this Revell 1/48 P-51 kit.
This is what I really wanted from the start-- a canopy with a separate, flanged base which I could mount to the body shell. The bare canopy didn't look right sitting directly on the body, so I think this'll be a good solution:
Much better, and I can more easily integrate the canopy and its base with the Avanti's hood and cowl bulge (yeah, I'm still holding onto that styling element):
I needed to figure out some type of chassis-to-body support, and while passing through the beading aisle at Michael's, I saw some copper pins which looked like they might work well for body support rods. The flat heads will touch the underside of the body in various places, while the opposite ends will be cut to length and soldered to the chassis. I have the body resting on the tops of the tires right now, so once all the body supports are in place, I will add a small round shim between the body and pin heads, which will both positively locate the pin heads and add a tiny bit of needed clearance between the tires and body. Here's a pic of the first pin in place:
The belly of the P-51 had what looked almost exactly like a late '80s aero-style snorkel scoop, and it was very close to 1/25 scale, too, so I assembled the plane's fuselage halves and cut away the scoop. I'm not sure this will remain, and I think I have to make the scoop's mouth flush with the rest of the body, but I'm going to work with it for now and see if it sticks: