That was our previous VHF-UHF mobile unit, the FT-8100. It was also mounted in the passenger side tunnel and used a dual-band magmount on the trunk lid.
We have found with HF and the ATAS that we have to mount the GPS antenna on the opposite side of the rear deck as it behaves weirdly when we're transmitting. The speaker is a 4" MFJ mobile sitting in the windblocker pocket between the seats.
Luckily there is nothing in the internal workings of the Rollerskate that's affected by HF and we're only running 100W. Next step is to use one of the jacks visible to the right of the FT-100D control head to try CW, perhaps with a knee-mounted key or bug.
Toys! Toys. Always fun.
BTW, I see you're into astronomy and photography also. Small world; so are we . We're both members of the Royal Astronomical Society of Canada, and have frequently sat out in deck chairs watching meteors and the SO did try something once a long time ago with meteor scatter and a helix antenna.
-- Nora VE2HAX (imagine a Canadian flag here) =======================and the Rollerskate (imagine a '99 gleaming silver Miata here)