I settled on an eFlite Taylorcraft as a good platform for testing the APM. The cabin is large and the wing has a window on top. I left the cabin side windows out to so I could reach in to flip the CLI switch and insert a USB cable when needed.
I used the laser at TechShop SF to cut a thin piece of clear plastic on which to mount the APM and all the sensors. (Attached is the Corel file.)
The goal was to make all of the LEDs, wiring, switches, and USB ports visible and accessible without removing any portion of the plane. This setup has worked very well.