Thanks Greg. The lens support is something I cobbled together. Mine has three contact points: the lens barrel, the lens foot, and the camera body.Beautiful shots Tom! Thank so much that was very helpful information! It that the RRS Long Lens Support system?
Although quite rigid, the unaddressed weak point is the ball head around which the entire assembly can rotate (even when tight). This can be solved by the addition of a Manfrotto long lens support which attaches to the portrait lens plate on the Pentax (L bracket needed for other bodies) and a tripod leg Long Lens Support - 359 | Manfrotto Global
Awkward, but effective, makes the 400mm much more attractive.
My Rube Goldberg device:
_IGP1179 by tsjanik47, on Flickr