Any books/sites to learn about 2 strokes from professionals?

[Challenger]

I would like to learn more about the 2 stroke engines, wondering if any of you know any places where I could really get to know the details about building them. Im not talking only about porting, just generally about two strokes, how does the angle of the channels in the cylinder influences the general performance? What about the shape of cylinder head? How can you set ("jet") your engine by changing piston-cylinder clearence? What are the exact differences between forged and usual pistons and how does the amount of silicon in them affect the engine?
These are some of the questions Id like to know the answer to + many more. Me myself have been struggling with stuttering of my WR200 engine on the very top range of revs - still dont have no idea what to do about it.
Im asking because the two stroke guru in my coutry is offering trainings for mechanics but the thing is they are very expensive and very far away. The only thing I found are some very old books with examples from another era. And it seems like the current proffesional two stroke guys dont really want to share their knowledge.

[Calum]

@challenger https://www.ebay.co.uk/itm/Two-Stroke-Performance-Tuning-2nd-Edition-A-Graham-Bell-Hardback/133565159585?epid=89650793&hash=item1f191a98a1:g:6XMAAOSwrYJfo80E

This is fantastic! I absolutely loved this book.

[Challenger]

@calum just bought a used one, will be waiting until it gets here. Do you remember what examples of engine are in the book? TZR250? generally any 90s yamaha engines?

[Calum]

@challenger Typically it's Rotax Engines, TZ 250 Engines and Suzukis.

I don't recall there being any examples of road going bikes, but I read it in 2013 so a long time ago now. I have since read the collection of other tuning books he wrote, they're very good.