Bill,
Rather than post directly here, I have put some pictures of my 600cc Aero Douglas petrol tank, before, after, and sketch, in the Reference section. Use this
link. Hopefully, this will make it easier for someone else in the future that needs similar information to stumble across it, and still provide an answer to you query (via the link.)
It is a 1936 petrol tank, but should be identical to what was being used in 1935, judging by the catalog illustration. I do have full size tracings of the panels on tissue paper, but copying these is problematic.
The plates will need to be contoured to match the curvature of the petrol tank, to maintain a consistent gap just larger than the thickness of the flange on the knee grip rubbers. To be quite honest, I forget if there are thick washers under the mounting plates, or if the gap is archived entirely just by contouring the plates to a more gradual curvature than the sides of the tank (the sides of the tank 'fall away' from the plate.) Those bits are buried in a cupboard and not presently accessible. Note- modern reproduction 'grips are cast in urethane and are not vulcanized rubber. They are very susceptible to tearing when trying to stretch them over the mounting plates.
The back of the hand change gate is contoured to fit tightly against the tank.
-Doug