As I recall there is a al gear to be cut on the crank near a counter weight a standar gear cutter would probably cut deep slots into the counterweight . One guy hear made his owne cutter that looked very nice .
As a result I looked up gear profile endmills . These exist but are special order atvthe time I looked one way or the other you will have some gashes in the counter weight . I did look into different means of installing counter weights. It would be best to contact Hogson directly . Have drawing pages on hand when you do he may have alternate ideas. He and his dad undoubtedly explored this a long time