There is a wealth of information on small engines on the internet.
Both RC Universe and RC groups has information on 1/2 engines. RC universe has a very nice Frequently asked questions (FAQ) on both COX and Norvel engines.
Cox engine forum is a dedicated form due to cox engines. There are a lot of control line activity there. If you need an answer they probably can find it. The group runs contests and events that can be done by video. very popular is Reed valve speed is popular. Rules are simple and you must video you flying the airplane 10 laps. Models must be semi scale and it may be an inspiration for anyone building a 1/2a for this contest.
Model builder magazine had series on reworking reed and other cox engines for maximum performance . They were written by Cox engine master Dale Kirn.
I will be breaking this down over the winter.