For what it's worth, I took the guts of a Powerhouse and moved it to a USA Deluxe body. SInce I have the TBX tone there was no way to fit the circuit board in the control cavity so I had to extend the wires and move the circuit board to the tremelo cavity after removing the claw and springs. (I was planing on blocking the tremelo anyway).
The circuit board fits perfectly and the battery is next to it in the trem cavity and only sticks out 1 mm. The trem cover fits over it without much of a bulge.
I put in a set of Noiseless Deluxes so it's about as close to a signature Clapton as I can get (w/o the claw and springs) and I really love the sound I get, plus the controls make so much more sense with 1 volume, 1 tone and 1 overdrive control.
It's crossed my mind to consider buying up Powerhouses, clipping the resistors and putting in the Noiseless VIntage p'ups and trying to get $600- $700 for 'em on eBay, but buyers don't seem to go for partcasters much. . .