I think one thing that is more important than all of the cutting, milling and timing figures combined is what is called The Fit. Because of the ever so slight tolerence differences in mass produced engine parts, most of the big time engine builders ( Paris, Hottenger, Roem, Rossi, ect) buy case lots of engines from Novarossi for example. Then they disassemble all of them ( were talikin 200 to 500 engines here) and by hand check the "fit" of say all the piston sleeve assemblies. Out of say 500 engines the builder may find 100 that are excellent fits. Then they will do the same check crankcases good bearing fit with no crankshft binding. Assembling all these "excellent fit" parts into an engine usually result in a mill that will daylight all the everyday dremel jobs running around out there. Then when they take do port work and timing work on an excellent fit.....watch out!! Thats why i dont really mess with doing my own mods any more. Unless you have the resources to do this fitting process, your just feeding sweet milk to a buzzard in my opinion.