Jig? Just slap it on the lathe and turn it down. Picco can break up over 5hp or so, I forget, and being 3/8 you might as well use a 3/8 rim which will fit most any saw big enough to snap picco chain.
What do you have in mind? Antique saw? I must be missing something.
Looks like it is stretching a good bit already in the video. Is it a bit slower than the last video you posted?