The internet is truely a wonderful thing.
Walter in answer to your question about where the control pallet is and how it is mounted can be found here:
TM-55-1520-240-23-9 CH-47D Heilcopter Manual scroll down to the instructions to '
Remove Control Pallet Sta 95' and '
Remove Control Pallet Sta 120'.
As you will see the pallets are fixed to the bulkheads (as Notchy advised) not to the floor, inside the control closet behind the LH seat, the pallets are secured to the bulkheads by 8 bolts. The manuals also describe exactly what flight control components are on the pallets. No radio/comms equipment at all was fitted to them.
Please bear in mind my first hand knowledge is distinctly dated, but (for what it's worth) my time and Talisker addled memories do concur with the information detailed in the documents above.