I'll tell you what I do, for what it's worth.
I use several compact CBs variously in three vehicles: a Jeep for off-road hunting trips, a pickup truck for camping trips hauling a travel trailer, and a sedan for regular highway trips to distant places.
Except for such dedicated ventures, I don't use a CB. And because of this fact, I don't permanently mount my radios or their antennas in my vehicles where they would / could just be in the way.
This also is why I exclusively use compact-sized CB radios wired with cigarette-lighter plugs for 12vdc power, and magnet-mounted antennas for placement on the vehicles' outside metal surfaces that are appropriate for best performance and are easily placed and removed.
Now, to FINALLY get to the question at hand: where to mount the radios so I avoid any drilling or alteration to the vehicles. I do this by fabricating a base that is suitable for operating the radios independent of any vehicle mounting point. The base I have chosen to use is home-made: a 4X4-inch wooden post material that I cut to a convenient length, perhaps 8 or 10 inches long, and onto this mobile base I screw on the radio mount. When the mounted radio is placed on a flat surface, it can be positioned so that it can be adjusted and used while driving on the road.
Even though I could place the radio and its mount somewhere it would fit on the dash or on the front console or in a (if unoccupied) passenger seat, I choose to place the mounted radio in the rear on the center of the passenger floorboard where I can reach back and make needed adjustments. I must note that this location is not good in the sense of being able to adjust the radio frequency, which requires actually looking at the radio to do, the rear floorboard placement is good for getting the radio out of cramped spaces in the front. And it works well for me since I don't adjust the frequency while driving since I exclusively have my radios tuned to truckers' channel 19 while on a trip, so I have no need to see to adjust for other channels. I can, however, without looking at the radio, adjust the volume, the squelch and the RF gain knobs because my simple compact radios only have those three adjusting knobs. This makes it easy to "see" and adjust with my right hand even while driving by reaching rearward and "feeling" which knob I need at any given time. IE: the first in line is the volume, the second is the squelch, and the third is the RF gain.
I know this "solution" to mounting a radio in small cabins without drilling holes is suited for me, but perhaps for no others. Nevertheless, I hereby present it for anyone it might be of interest to.