A simple method for ensuring constant thickness is to make a jig.
The jig is made by placing two strips of electrical tape on a flat surface. Five strips will result in a .5mm guide. Ten will give you 1mm.
Place the part between the strips and remove the excess wood using a chisel taking care to not cut into the tape.
Work slow and take small amounts of wood at a time. If you cut the tape, peel off the offending strips and reapply.
Lou
per my comment in your main thread of the build. Excellent.
Fraser
Thank you Fraser.
Lou