I am building a warbird and they tell me to mount the reciever and batt with foam back to back on a plywood plate right back to back I tested range with engine running and have no problems

Tim......I'm not sure about mounting the battery next to the reciever.........I mount my battery generally as far fwd as possible........due to Warbirds most of the time need nose weight.......I prefer an exposed antenna outside the fuselage so I put the reciever near the aft part of the canopy......exiting behind canopy and to vertical fin.....some guys run a plastic tube inside the fuselage and put the antenna wire thru it.........definitely keep the battery and reciever well insulated with foam....and make sure it range cks good with the engine running as you have done......Regards.....Bill.......