[Walt Fricke]

I'm thinking you may be overthinking. I have run straight cut gears in this case with no problems. The oil under pressure on the iron IS cover plate keeps the end of the shaft from scoring or otherwise rubbing too much on the plate. I can't say I ever gave any thought to what keeps the shaft from moving toward the oil pump, though the circlips on the shaft ends appear to be up to that light task.

Seems to me that allowing the IS shaft to float a bit, with restrictions which prevent enough movement for any interference or misalignment of the chains (which, themselves, should exert a sort of centering force. When you are measuring chain wheel parallelism, you push the shaft into the engine to take that measurement.