um i would not do that!! i've never heared of anyone using wood/shims to raise a bike. this is mechanics, not carpentry!
if you really need to raise the bike a lil if anything turn your coil on the rear shock!!! :headscratch
1. If you have rear ride height adjuster. Unbolt the top nut and linkages and
itstall shims. Install back as reverse instruction.
2. Go to your local fabricator and ask them to fabricate a new linkage with
multiple holes in it. In that way, your can play with different height with
3. Adjust your shock coil.