This is how to mount the preamp into your guitar. The guitar that I mounted it into is an Ibanez EX series as it is very typical of the size of the wiring / control cavity. The trick is to build the components onto the tag strips keeping it very tight and not leaving long component leads. Lay the circuit out flat and cover it with electical tape. The batteries fit on top and are held in place by replacement of the cavity cover. You can also change the cable input jack to one with an inbuilt switch so that unplugging the guitar lead cuts of the batteries.

It would be even easier to mount the preamp into guitars that have the control space underneath the pick guard. The next guitar to tackle will be an acoustic but I do not think it will be too hard mounting the preamp inside and hidden from view.