Nice job. Can you show pics of tools you're using?
Five things really,
Harbor Freight electric die grinder with 6” double cut burr (the burr is not from HF)
Magnetic LED light (very, very important to see)
6” spring inside caliper, also HF, used more for comparing than actually transferring measurements
Straight edge for the chamber mod
iPhone, Mark’ videos, and a Google Sheet and slide instruction I made from his videos.
As well, I’d say half the battle was finding a machinist who would take care of the guides correctly, de shroud the valves in the chamber, and cut the valve angles and widths Mark instructed. 30, 45, 60, 75. The width of the 60 is important, and then only open up to 86-87%. Some open theirs up more, but you can’t put metal back in.
On the exhaust, the width of the 45 is important.
Another video which is very helpful is the one from David Vizzard when he was much younger and talking about mini cylinder head valve angles and porting.