I like your suggestion too. A way to make easy thrust adjustments is to sand a wedge from good plywood that won't crush too much.

The way I do it is to spray glue an appropriate piece (usually 1/8" aircraft ply to the edge of my glass work bench. I use coarse paper or a tungstan sand to rip it to shape quickly. Then I progress to finer grits to smooth it out.

I drop the wedges in a can of oil-gase polyurethane to soak an hour to over night. I then hang it on a wire through one of the mounting holes and use a paper towel to soak up the excess puddle that runs to the edge.

After it's dry a light sanding to flatten the part and it's done unless I sand through the paint in which coat I'll brush or spary a finish coat. Give it a week or so to fully dry and you're in business.

The biggest problem with adding shims or wedges is that the spinner won't align with the cowel any more. Whenever possible I trim the model without the cowl mounted and then add the cowl later. Adding the cowl does change the aerodynamics a bit but I haven't found that it makes a difference in the thrust adjustment.

- Paul