he did some lightening to the 4.2 , he may have lightened some with the gold case also not sure, I have one of the older gold versions and it is heavier than the new ones including the fox 4.2.
If you want info on them just go to Fox manufacturing or call them and talk to Charley Thacker or Herold Willy. on the fox engines
Kangky can tell you about the Brison.