I've installed a number of "mast kits," and I am not really impressed with the design of the factory made solution.
I don't think the NEC discusses this issue, so i took a look at our local utility's specs:
"Periscope structures projecting over 30" above the roof must be braced....Bracing, when required, shall consist of two galvanised steel members installed at approximately 90 degree spread. Minimum size brace shall be 1 1/4 x 1 1/4 x 1/8" galvanised steel angle. Periscope bracing shall be anchored through the sub-roof with minimum 3/8" galvanised carraige bolts."
The accompanying artwork also specifies the bracing to be attached 10" below the weatherhead.
Ironically, the "mast kits" that I've been using rely upon 3/4 RMC for bracing members, and anchor to the roof with lag bolts (that might be 3/8").
Off the cuff, I would guess that this man's solution is as strong as the commercially prepared kit. It is certainly securely anchored to the mast with those multiple mineralacs. It is also quite a bit more expensive than the commercial arrangement I've been using.
