Well, based on the way my Lady Bug flew tonight, I concluded that some downthrust is in order. The only problem is that the TD .020's backplate mount has only two screws at 180° spacing, so my usual method of adding washers between the backplate and firewall won't work. Perhaps I'm just tired from a long day, but I'm fresh out of ingenuity. I've been staring at this for a half-hour and can't think of a good easy way to add downthrust. I thought about making a little shim out of sheet styrene or some other fuelproof sheet material and placing it between the top of the backplate, but it seems like it would distort the backplate and be less than secure. The only other thought I have is to make a new plywood backing ring like it mounts to now and sand the desired angle into it, which will be a pain, time-consuming, or both. Anybody got an easy solution? Maybe I'm worrying too much.

An easy way to make a ply shim is to place a piece of ply between two music wires of different thickness and then sand until it is flush with the wires. I clamp the music wires to my workbench and use some double sided tape to hold the ply while sanding.

Thanks a million, bipe! I knew there had to be an easy solution, I just couldn't think of it in my overtired mental state.[:@] I tried a few shims cut out of GWS prop blades and sanded to shape last night but I could see it distorting the backplate at the screw holes, as I feared. I don't have any of them fancy angle sanders, and my only tool for cutting oddly curved shapes is a jewelers saw, so I tend to think things are harder than they wind up being......thanks again for the music wire tip, that's exactly what I needed.

You're welcome. It works for making ailerons or trailing edges too.

Worked like a charm, not that I'm surprised. Too bad I just remembered now that I have a little orbital sander that would've done the job in half the time it took me by hand. I need to get better bar clamps, though. Those little round feet want to walk on the underside of the bench too much when I start putting pressure on the wires with the sanding bar...I need these:

GOOD GRIEF! What brand is that? There's more beef there than a wendy's burger!

Why, that's the Binford 5000XL, Arr, Arr, Arr, as 'Tim the Toolman Taylor' would say! It's a Craftsman 12" with reversible jaw(spreader), actually. I've got a bunch of ancient cast Bessey bar clamps, they're fine for general carpentry, but no matter what I put under the stupid little round foot, they walk when I'm doing finicky little stuff like this.