I know an army signals unit that used to have hardtop FFR Landrovers with the canvas over the top, never quite worked out why, whether it was to keep the interior cooler or whatever, not to sure. Our hardtop FFR's were so heavily camouflaged in position it wasnt identifiable as a Landrover and wouldnt have mattered.
Going into an AlienFTM moment! We were on an exercise at RAF Chivenor, when it had just been closed, providing the comms for another squadrons Tactical Evaluation (TACEVAL) we had a large quantity of Bedford trucks and Landrovers and a Satcom Landrover.
We were required to setup our equipment on the side of a large building that was being used as an HQ, so we were limited to camouflage options, so we put up tarps from under the guttering of the said building, in a very large lean to effect, with a drop for a wall, making sure it was all pulled taught, the generators and satellite dish that had to go outside of the tarp "building" we camouflaged with hessian and cam net, to give a bushes and vegetation effect.
During the exercise an "Enemy" Jaguar done a high speed low level recce pass and the pictures taken processed by the photo interpreter intelligence types. Ours was the only unit on that exercise where they couldnt identify quantities or vehicles in use, or infact any of our comms kit including the satellite dish, they knew something was there, but that was it!
I seem to remember that the units who were being evaluated didnt fare so well...