i saw blair's book and paged thu it is basically just a bunch of math equations. You might find some good info in there but ultimately not going to be as helpful as the other 2 books.
it starts to get a bit to much into specifics of certain bikes and setups. For old little bikes using points and without gears like ours alot of it is just not applicable.
equations are still only as accurate as ur grinding hand, and ur building skill in the end, i find simple math helpful as a starting point, but ultimately trial and error will serve u better when it comes to mopeds.
even in bell's book he says the exact exhaust numbers are all highly secretive and making perfect pipes is somewhat of an art.
many tuners say the same about needle selection, and portwork is definitely more of an art, especially on a moped where u basically start with complete crap. its best to understand how to design a 2 stroke motor rather than what those books tell u about portwork on existing bikes that already rip. Mopeds are so restricted from the factory u might as well start with a chunk of metal lol. I think that's the one point that all the 2 stroke books are missing, and what sets mopeds into their own tuning category.