I recently bought an older model mvvs 35 that came with a CH ignition. The hall effect is held in place by a clamp around the case. What is a good starting point from TDC place the sensor?

Thanks

It depends on the CH advance. If it has none, then start at 20 degrees before TDC. You will probably end up running full bore at about 25 - 28 degrees.
If you use the piston position method, start with 0.8mm BTDC.
Do not advance ignition timing beyond the point of best power. It will make for a mean engine if you do. Better back off very slightly. This allows for higher rpm as the prop unwinds.