I put #1 cylinder in TDC and noticed that some marks on the prob hub appeared to line up with the case seam. I then lined up the magnet shoe on the flywheel with the edge of the Magnatron. This is supposed to be the Magnatron firing position at 28 deg BTDC. Another set of marks on the prop hub now lined up with the case seam. Coincidence? - maybe.
I hightllighted the two marks on the prop hub as TDC and 28 deg BTDC. I also marked a tooth on the right side of the flywheel and a corresponding mark on the case to indicate the TDC and 28 deg BTDC positions. Once the engine is running I can adjust the case "B" mark based on Magnatron timing light indications, then adjust the electronic timing with the timing light to match the "B" position. Both systems should then be firing at the same time.
Using the flywheel marks with the timing light keeps me away from the prop.