There is currently a 1/72 scale resin kit on eBay with a buy it now price of $43. Probably molded from the same drawings that you are using but it could serve as inspiration. Are you using a catalyzed paint for the final coats on the plugs? That should help with the hardness. I went back and read your first post. I'm pretty impressed that you are shooting for that much detail on what is going to be a relatively small model for a twin engined warbird.