Musings on an open thermin build

OK so an Open Theremin V3 kit is headed my way from Switzerland as my first go at building one of these and I've found a nice old 3 bottle wooden wine box to mount it in amongst my collection of stuff squirrelled away in case it comes in useful. Which got me thinking as to what could be done with all the empty space there will be inside the box.
So thought turned to the little valve (tube to most none Brits) headphone amp that isn't getting much use, built from one of those ebay kits a few years back and with some matched NOS mullard valves in it sounds really nice through some active speakers in that valve amp way. 
Does anyone know if sticking something like that preamp board in close proximity to the open theremin board and slap bang between the antennas is going to cause any problems?
Also depending where in the box things get put in the box there could be anywhere between about 5cm and 15cm of wire between the open theremin board and end of the antenna rods, is this within the bounds of OK or will I need to tweak the antenna length a bit.
 

"Does anyone know if sticking something like that preamp board in close proximity to the open theremin board and slap bang between the antennas is going to cause any problems?"  - dtalbot

The heat from the tube(s) may cause drift.  If there's any AC associated with the circuit it may get picked up by the antennas.  The conduction of the board and attached wires will affect the Theremin fields.  If you want to go this route maybe stick the Theremin circuit board in there, try it out for a while, and then experiment by merely placing the preamp near where you're thinking of mounting it, and see if it causes trouble.

"Also depending where in the box things get put in the box there could be anywhere between about 5cm and 15cm of wire between the open theremin board and end of the antenna rods, is this within the bounds of OK or will I need to tweak the antenna length a bit."

The wires going to the antennas will be the same as antennas.  Designs that use series EQ coils should work better for widely spaced antennas as the coils can be placed near the antennas, and the drive sides of the coils tend to be lower impedance.  But 5cm to 15cm doesn't seem egregious.  It will add to the capacitance though. 

Thanks Dewster. I will certainly do the experimentation, with both the preamp and the wires. The build instructions do say you can use a stiff wire to connect the board and the edge of the box but do also say don't make it too long. Depending on how I end up laying it out I may not even need wires as looking at the pictures of Coralie Ehinger's Open Theremin the straight horizontal sections of the antennas on hers would easily clear the edges of the box I have. 

The preamp is a 12 volt AC feed so good point on that, i plan on the tubes sticking out of the box (just because I like the glow!) so hopefully they won't cause too much thermal disruption. but maybe just more sensible just to stick the preamp a few feet away with the speakers