Hi Josh/Mike
I have no issues with the standard BSA breather, properly set up it works very well, It is vital to have the cork disc the right thickness or it wont work.
in one of the articles he goes on about reducing leaks from the top end by having a rocker mounted breather
The pressure or vacuum is the same in all parts of the engine!
Rockerbox to head, gasket leaks are usually caused by damaged faces, bolt holes filled with crap or I believe poor head steady mounts, I think the head steady mounts can cause movement between the rockerbox and head causing leaks
To this end I have fitted an isolastic type bush between the headsteady and the rockerbox, no problems so far
Regards
John O R