Hi All,
I just posted about this in the Pentax Lens and Accessory Forum, and it's relevant to this one, so I'll post here also.
There are two lenses that I have that pose problems for support with the Q-- the A* 200 f2.8 and Tamron SP 180 f2.5. I'm sure that one of the collars for the Pentax Adapter would work, and the mount of the adapter is strong enough to not cause problems, but the front elements of these are 77mm and the lens is very front heavy. Also, these lenses really have no space where a collar can be mounted on the lens.
My solution is a 6" Hejnar Photography Lens Support
6 inch Lens Support Package [LLSP4] - $85.00 : Hejnar Photo Store, Serving Your Professional Photography Needs
I already had the double back-to-back clamps for some of my macro flash bracket applications, so saved some money there. I also always have an Arca plate mounted on my Qs.
It's pricey, but fits my needs well, so worth it for me. With this, I have a quickly adjustable lens support if I need it, and the double Arca compatible dovetail rail allows me to balance the lens/camera on the head, which makes it a lot easier and faster to sight and lock since I don't have to fight the weight.
Here's a quick snap of the setup with the A* 200/2.8. A Velcro strap, heavy rubber band, or small bungie cord can be added if you need to use the camera in portrait orientation.
It's not for everyone, but it's a solution if you have heavy lenses with no tripod collar.
Scott