I really like my 300 tele for my P67, which has a collar mount. But it is a quite a beast compared to Hassie 6X6 lens of equivalent focal length. It's a nice lens for use in the wind or quickie road shots. But a tiny Nikon 300 M lens when used for a 6X7 or 6X9 roll film back is more versatile and far easier to tripod-stabilize. I never use traditional pan-tilt tripod heads for these kind of applications, but only for shorter lighter 6X7 teles like the 165/2.8 Pentax. The ultimate mount for my 300 EDIF Pentax is a laminated hardwood & phenolic bar with two screw positions : one for the camera body, the other for the lens collar, which in turn is bolted directly to the platform top of my larger Ries wooden tripod. It gives me a similar angle of view as a 450 lens on full 4X5 film.
My CT3472 Feisol CF tripod (which I've modified for direct platform top attachment) gives me plenty of rigidity, equivalent to my larger Ries, but not the same sheer bully mass in terms of shear-wind resistance or jabbing the spikes solidly into the muck (both tripods have spikes). But I bought the Feisol, which is less than half the weight of the Ries, for sake of inevitable aging issues, as well as for greater travel compactness when collapsed. Likewise, I have a complement of both a smaller Ries wooden tripod and smaller Gitzo CF for 4X5 and ordinary MF usage. But whenever realistic, I prefer Ries.