I tried using spacers in front of the fence and doing multiple passes
with my 3 1/4" panel raising bit in my shaper. The cutting was so
clean and easy during testing I tried just powering through a full
depth cut in a single pass (Pine). I ended up cutting all 24 panels
this way and felt totally safe.

The only issue was a slight bit of fuzzing on the cross cut with the
sharp edge at the face of the panel and a slight brush with some 100
sandpaper cleaned it up easy.

I suppose holding off 1/8" on the first pass and doing a clean up pass
would have mayde for a little smoother surface but for this rustic
project it was more than smooth enough.