Ralph,
You probably had a very old MVVS which had the small black plastic potted ignition with flange mounting and 4 cells NiCad for Voltage. A lot has changed since then. The latest ignitions have two magnets, one leading the other by 120 degrees. These should be used with 6 cells NiMH or two cells LiPo for the S- and L-versions (6.5 - 8.5 Volts). The P-version needs 3xLiPo or equivalent number of NiMH cells (9x)
For a manual of the latest ignitions, see http://mvvs.nl/MVVS/ICU-V1.5.pdf

The RC-Excl ignition needs about 40 degree lead in the single magnet, not 28 degree. It needs the extra 12 degree for it's timing calculations at full rpm, and retards about 35 degree at idle rpm. They need a fairly fast starting flip in order to retard well and not to kick back.
At least the ones I tested were timed like this. Very good ignitions indeed. I made an adjustable magnet ring to experiment with the timing. 40° magnet position BTDC was best for low idle and WOT running.