Techman
I suspect that it was indeed R/C....... for the take-off and up to cruise. I've just realised why Maynard Hill's name rang a bell. One of my old R/C Annuals carried an article on a previous record of his - the R/C altitude record.... something around 29,000 ft.
I wonder if he was using the same sort of auto-pilot which he had then - an extraordinary device using sensors on the extremities which measured the static electricity voltage. It appears that there is a very marked ramp of S.E voltage relative to the surface directly below and that voltage difference was used to drive the pitch and roll servos. The sensitivity of the device was such as to allow full control with the C.G. at some ridiculously aft position (quite impossible for manual control). Because the inputs are relative to the surface, mountain flying or similarly uneven references are a no-no.
Anyone have anything further,please?