What ever you choose, make sure everything is anchored well. As stated several times above, anything not well secured can become a "missile hazard" in a collision.
Something heavy, like the RF deck for these radios, really needs to be secured well. Double sided tape, velcro, etc. is really risky. I don't even like using the cheap sheet metal screws that come with most radios. I take the time to through-bolt everything with nylock nuts and large washers or a reinforcement plate when going through plastic. The roads in this part of California are in pretty bad shape, the vibration from hitting pot holes, etc. will quickly strip out the sheet metal screws. Taking a vehicle off road is even more harsh on the mounting.
You can get away with velcro or the really strong 3M double side tape for really light stuff, like the control heads on these radios. Not ideal, but it'll work.