Sounds great! You mentioned the shielding making your guitar loudier in RF noisy environments. I assume that you are grounding the shielded cavity- right? To connect the shielding to ground you can first put a piece of copper foil down into the cavity and coming up to the top surface of the guitar where it will be in contact with the foil on the backside of the pick guard.

    You might want to check out the suggestions on John Atcheley's site. He has devised a method of keeping the audio signal returns isolated from the shields and pot cases with a large value poly cap (like 1uf or 2.2uF at 400 to 630vdc). There is a link to his site on my schematics page:

http://www.techaccessinc.com/blueguitar/

Steve Ahola 

  

obviously all the wiring in the guitar is star grounded as the great article from J. Atchley suggest.

I use a screw into carbon painted cavity star-connected to all the shields (pickguard, controls, pots, switches) and the ground in output jack. The ground side of out jack is the ONLY point in the circuit connecting negative side and shields.

Have you mesured with a ohmmeter the resistivity in Stew Mac paint? I am intrested to know if this is better than mine.

concerning the cable, I checked out some cable stats and noted that braided wire may only offer 80% shielding whereas foil scored like 98%. Good point Kursad yet 

  

Lower quality cables have less than 100% outer braid coverge (as Evan pointed out), so there are obviously small "holes" where an RF signal can be coupled to the center conductor. Use some George L's cable or RG-174 coax as samples of cable that have total shield coverage.

Don't forget that all the unshielded conductors strung between pots, pickup selector switches, and sometimes the output jack (typical of US Fender guitars), pick up a considerable amount of garbage. The control cavity, enclosed in a metal shield, is silent. 

There is even a difference in hum pickup on humbucker equipped guitars, like Les Pauls. Why do some of the earlier ones have actual formed metal "cans" in the control cavity and around the selector switch? 

Cavity shielding definitely makes a difference. But it must be a continuous shield to be very effective at hum reduction. All compartment shields must be electrically connected to the guitar's ground system. I recently added copper foil cavity shielding (all tape seams soldered) to a '52 reissue telecaster with stock single coil pickups. The owner can't believe the difference in hum pickup level the shielding has made.