Maoraigh has a lot of experience in flying around lumpy terrain and I have a little too, but I recall one flight North over the Grampians when the owner's voice from the rear seat of the Cub asked "why are we descending?" My reply, "because we can't outclimb the sink!"
He and I both knew one who died, along with his passenger, on a mountainside in poor weather probably due to downdraft on the lee side.