Hi olev,thanks.
The superblend is larger diameter so you just need a bigger hole [obviously careful setting up and not using a knackered power drill/dremel]. Its fairly straightforeward for a machine shop but requires some careful measuring and depends on the timing side set up.
I think the hole needs to be slightly deeper as well as you end up with little room for the crank seal. The cage seems larger as well. I addressed this by making the fruit bowl /alternator thing have a bit of diameter to extend the seal area. [easier to see in the pic ]
The back side of the fruit bowl is also a tight fit on the crankcase, hopefully fooling the bearing into believing it has more meat supporting it.
I have never done this before but several people have successfully so should be ok .Provided its under 850 and don't go too far over 9500rpm.
Regarding the alton, I agree the supplied belt really does not look up to the job.
The srm belt front pulley is taper bored for the original dynamo, the alton has a 13mm parallel shaft and key, so once again you need a bigger hole and a keyway.
Hope this is useful.