I just answered this sort of question on an Ercoupe forum, though that device was for a Garmin 195. However otherwise everything should work. I know you said you don't have room on the panel, but...there's always room, yes? The vehicle (panel) mounting base itself doesn't take much room.
The RAM mounts consist of a few different components, which I'll summarize for most purposes as:
- the vehicle mounting base type (for yoke, flat surface, floor mount etc.);
- the arm;
- the base for the cradle;
- the cradle for your device.
For a panel mount I used a flat surface base+ball that screws or bolts to the sheet metal (no suction or adhesive):
RAM 2.5" Round Ball Base with the AMPs Hole Pattern & 1" Ball, Product Number: RAM-B-202U
For the arm, choose a length you think convenient:
RAM Double Socket Arm for 1" Ball Bases. Overall Length: 3.69", Product Number: RAM-B-201U
or
RAM Short Double Socket Arm for 1" Ball Bases (Overall Length: 2.38"), Product Number: RAM-B-201U-A
or
RAM Long Double Socket Arm for 1" Ball Bases, Product Number: RAM-B-201U-C
For cradle base,
RAM 2.43" x 1.31" Composite Diamond Base with 1" Ball, Product Number: RAP-B-238U
And finally the cradle for your GPS:
RAM Cradle Holder for the Garmin GPSMAP 176, 176C, 196, 276C, 296, 376C, 378, 396, 478 & 496
Product Number: RAM-HOL-GA7U