Just FWIW...
Kenwood makes a platform to mount both radio and control head to for the TS-480, but I see no reason why it wouldn't work for the '710 also. Everything on one 'chunk' sort of with a handle to carry the whole thing. Unfortunately they don't sell it in the USA.
I made one from plastic for the TS-480 and am thinking about making one for the '710 also. The main draw back is that it makes that 'chunk' rather large. Fine for portable stuff but no idea how you'd fit it into a car.
I also had the idea of being able to move the '710 from the car to the house (just one car). I have mine under the passenger's front seat with the head mounted on the dash. There's just the one control cable to 'un-string' so it wouldn't be too inconvenient. The mic cable I made an extension for so that's not a biggy. The absolute most important thing for me is labeling all the @#$ cables going to the radio (speakers, etc). It isn't the only radio in the car so it can get confusing very quickly, you know? I did that for a while but found a good deal on a TM-D71A! The '71 and '710 are exactly the same radio, just different control heads (TNC in the '710's). So, I don't have to move the radio anymore. All things considered, if I can find a more remote mounting location than under the seat I'm going to do some shifting of things around. There are a couple of storage places in the back of an HHR that would hold things, I think. The primary 'watch it' about doing that is cooling for the radio, there's no air circulation at all in those 'boxes'. So, ain't been done yet.
Aside from the 'whine/snivel/crying' about how hard I've got to do things, the important part in all this is that labeling of the @#$ cables! Do that! (It ain't the biggies, it's the little things that'll get you...)
- 'Doc