Today I discovered where (I think) the mystery parts fit. They are angles from the inner skins to the firewall. I have some CAD drawings of the fuselage & they show a piece (right side only) not mentioned in any build manual. One hole needed to be added to the firewall to match that angle & I decided to install the other angle to the left side. That required match drilling the firewall to all the holes in the angle. I can now start disassembling again making some minor alterations to various parts as I go prior to making a concerted effort to get the final deburring, priming & assembly done. I also restored my very old David Clarke H10-40 headset with new foam linings, seals, covers & headband. It looks good but still weighs 20 ounces! I think I'll lend it to GAM & get a lighter version for myself.
The only reference I can find to the angle in question
