With some fear of sounding like a smartypants...sell them both and buy an all mode/all band like an Icom 706, or a Yaesu FT857. It is difficult enough finding room for just one remote head, much less two complete radios, even small ones like yours.
And there is a safety issue too. With out due causion, any mounting scheme you use to make R&R simple yet safe is probably going to be just as intrusive as the complete radio would be.
Good Luck in any case.