@Lorenz I am not sure I can be much help – as I don't feel that I am technical enough to answer your questions.
I can share my experience to date though.
I bought a MK3 which came to me without the electric start working.
The bike had a PODtronics reg/rec and a Boyer MKIII electronic Ignition.
I reinstated the starter (there was no solenoid or heavy cables) and immediately I found that when I was starting the bike, it was back-firing really badly.
I fitted a Tri-Spark electronic ignition, and all those issues went away straight away.
However, I then found that I was getting the flatspot between 3,000 – 4,000rpm as described in the Tri-Spark document.
So, having read some of the recommendations and reviews and being told by a dealer that the Tri-Spark MOSFET reg/rec was the best thing on earth, I subsequently bought and fitted the shiny blue MOSFET reg/rec.
I fitted the same unit to my 750 a couple of months later, as I was really put off PODtronics at the time.
Earlier in the year I replaced the belt on the primary drive, and made the mistake of running it for a couple of weeks with the primary cover off, as I wanted to make sure the new belt was tensioned properly, and tracked true.
I say made the mistake, because by doing this I noticed that my alternator stator was getting too hot to touch, which got me panicking about the reliability of my alternator.
I spent a couple of months watching eBay, and bought a couple of New Old Stock zener diodes at a very good price, so have now fitted one of these to my 750.
This has been a revelation, as the alternator is now warm when running, but is not hot at all, so I am very happy with what I’ve ended up with.
My friend has an Alton Starter, and we had a lot of trouble with the woodruff keys shearing.
Over quite some time, we narrowed this down to the spacer not allowing the sprag clutch rotor assembly and triplex sprocket from clamping together tightly. So, all the starter torque was going through the woodruff key.
Now we have found the problem, and fixed it, I have a nasty feeling that the little plastic pins will be the next problem. I think he has fitted six now, but I get the feeling it will come back to bite, and we will end up doing the “Yves fix”