The 2 most critical things are:

Getting the trigger wheel sensor set up correctly on a robust mount.

Resistor type spark plugs. Non resistor types are going to cause interference with the trigger wheel sensor.

@Roger V : so the answer to : Speeduino can it handle injection as well as ignition with only the crank triggerwheel 60-2 is : yes !!!

I was cycling this afternoon (as usual) and I got the following (good ???) idea : I drill 5 mm holes (in the 60-2 config) in the flywheel, glue strong round magnets in the holes, which stick out 1 mm and put a HS at the side of the engine. This HS is one for soldering on a board. Its tiny small, has almost no mass and can easily be fixed on a small plate to be screwed on the bellhousing fixing.
I use already such HS, (glued to the brake housing) which is also magnet operated, and which switches a cooling fan at a car speed lower than 40 km/hr. Works very fine and the distance from the HS to the magnet is not very critical. Of course it should be powerful magnets. They are cheep and drilling holes in the flywheel is also easy.

@Roger V : is it absolutely necessary that both high and low part of the block tension are equal in duration ?

The HS next to my thumb.

You don't need magnets. An automotive hall effect sensor has a magnet built into the sensor, and detects how much the magnetic field is distorted when the sensor is near ferrous metal. Therefore it will detect holes that you drill in the flywheel.

I would suggest 36-1 is sufficient. Then The hole centers would be every 10 degrees. Dont forget the missing hole.

The hole needs to be wider than the active width of the sensor. I would think 8mm would be fine.

All the sensor is looking for, is a change of state.

Accuracy is important.

@Roger V : I have not such a good experience with the mounting of an automotive sensor (inductive) which I have now for the 1-2-Spark ignition. It should see a metal pen (6 mm bolt) which is turned in on the top surface of the flywheel. The airgap is too critical, max 0,5 mm. Imagine the high speed developed at 4000 rev/min or more !!! Therefore a see a a lot of benefits in mounting an HS which has to see magnets. Herewith the airgap is much less critical, 1,5 to 2 mm is sufficient. The mounting of a very tiny HS is also less critical then mounting an automotive sensor, due to less weight and dimensions. Vibrations of the engine has less of an effect on its stability.
Your suggestion to only have a 36-1 pattern seems to be OK for me too. Its at least less work to drill the holes.

You must have a good glue otherwise your magnets will be satelised.... (centrifugal force, heat, vibrations).

@AZL57 : The magnets have to sit tight fit in the drilled holes (eg : hole is 4mm deep, magnet is 5mm thick, assisted by an excellent glue.
I already have glued a HS which is encapsulated by a plastic tube to the housing of a brake. You can imagine that brakes vibrate heavily and become hotter then an engine. No problems encountered yet.

The sensor running < 1.0 mm from flywheel isn't an issue. Though I think mine may be bigger than that.

Theee was a chap on Speedy that built a sensor in the same format as yours. He encapsulated the sensor in resin, and placed it in the crank casing of his motor cycle. I've asked him for part numbers.

@Roger V : thanks !