Craig,
I have the Trig TY91 8.33 Khz radio in my 6A for nearly 2 years and it is an excellent unit.
The control head which is 2 1/4 inches easily fits in the panel and because of its short depth can fit nearly anywhere.
The main radio I fitted under the passenger seat near the antenna. However it could easily be fitted behind the baggage compartment. I have found the Trig company support to be excellent if you have questions or require the radio to be updated to the latest firmware.
Barry RV6A F-PRVM