Dan......You are correct in that this would not be a sustainable RPM.....I don't believe Pat Downs would state that it was sustainable....I'm assuming you are using the engine in a street vehicle, so a "sustained" RPM, is probably around 4,500-5,000RPM.
With the extra valve spring tension, and the thrust loading associated with it, engine life will probably be somewhat shorter than one designed for 6,000-6,500RPM......
It's the old, old, saying..."Speed cost money. How fast can you afford to go?"
If you only touch redline occasionaly, things should live a reasonable period of time, so relax and enjoy it, if you get it....
