28 degrees is good, all my conversions are timed at 28...Small ones don't kick back hard enough to bother with spark retard for starting...
The ones I did like that were a long time ago, the BC260, 340, and 430 Brushcutter engines...the case looks the same but the magneto setup was different...I cut the crank off in the rear and put my ignition circuit in there, with the spark coil from a G62 on the front like the new G26....Now that you have a lathe there IS a better way...
Check out the front of this G26...See the ring on the case behind the hub ? The hall sensor is epoxied in it, a slot in the bottom..You can see the wire coming out...The front of the case can be machined for an aluminum ring..That one is 1 3/4 diameter and about 1/4 inch thick..Make the hub with the taper in it to the same 1 3/4 diameter at the bottom, and whatever you want the rest of the way, a little longer than the bottom of the thread on the end of the crank..You want enough of the thread sticking out for the nut to hold it on the crank...