I've see people use a large tubing cutter to cut the housing. Makes straight consistent cuts. Then beveling of the ends and clamping it secure and straight just like in the video you posted. I had a shop narrow my 8.75- had them do everything.- new ends and a drain plug welded into the housing. New tubing ends and new green bearing installed. The shop used Moser to cut and respline the axles. It was not cheap. Total came to $700.