So here's what I did:
-- My VOR I mounted on the bottom of the tailcone under the HS so I put a doubler in there
-- Installed the Van's AHRS shelf per the shelf plans to the left of the elevator bell crank (I have my Transponder mounted to it)
-- Installed Van's ELT mount on the left side of the tailcone about a foot aft of the baggage bulkhead and between the F-1047 D & E stiffeners.
-- Installed SteinAir's magnetometer bracket to the front top of the F-1008 fuse frame and the ELT just in front of that
My #1 COM antenna (a few inches aft of the baggage bulkhead) is mounted on the top of the tailcone so I mounted it and its doubler much later as I really didn't know where the COM antennas were going to go at this point in the build. The same is true of the transponder antenna which is on the bottom of the tailcone just aft of the baggage bulkhead and offset to the right of centerline.