I know about the SIU way, but I have come across a "Y" cable that is for two Astro Spectra's. In the software under the "Advanced II" tab you check the box for a dual band unit and designate one radio as primary and the other as secondary. This is usually also referred to as the green radio and...
I took out the small DIN box that was below the radio and my dualband Yaesu FT-5100 fit right in there.
I also have a 1ghz laptop mounted on a nice sturdy RAM Mount and the base is bolted to the passenger seat bolt. Very secure mount. The neck is adjustable in case I need to push it out of...