Ergorest vehicle window pod (1 Viewer)

I have just been through the posts regarding the above. I am looking at it mainly as a vehicle pod but have a few questions for those that have used it.

I will be using it with a 400mm lens and/or Leica digiscoping outfit.

1. Is it worth it and do you still use it?

2. How does it fit? The pictures I have seen seem to show it resting on the car window and on the inside of the car, is it stable like this?

3. Most vehicle windows are not level/straight so if the above is true can you level it?

4. What kind of head do you use and with what equipment?

Apart from the Kirk are there any alternatives?

Many thanks

Pete

[I know this is an old thread but in case you are still wondering...]

1. Y-e-s. It's better than a beanbag because you can move the lens MUCH more easily and even zoom with it. It's more hassle to set up than a beanbag though.
2. The "top" arm has a groove. Roll the window up a little, put the groove on the glass and the other leg against the car door (on the inside...). Very stable. On a landcruiser in the Masai Mara I could leave the rest in place (though remove the camera!) whilst driving around.
3. Use a ball head
4. Arca Swiss - used with a Nikon 80 - 400 VR and Sigma 120 - 300 2.8 (plus teles). For the Sigma I also use a half Wimberley. This whole combo makes a heavy lens a JOY to use (as well as allowing me to track running Cheetahs....)

I use the ergorest with a manfrotto 222 pistol grip head and it works extremely well, both with the Sigma 50-500 I used to have and the canon 100-400, even when using 2x convertor. Besides clipping to the inside of the car window, I have used it other ways, When in Kenya last year our landcruiser had no windows, but had a small platform on the side, by doubling over the ergorest, it stood firmly on this, cos the 222 head is 22cm high, this brought my lens to ideal working height from the sitting postion. I have also found this format good to rest on the seawall when coast watching, saves lumping around a full tripod, I have also on occasion clipped the lip over the chest strap of my lowepro S&F harness, with the lower part resting against my stomach to form a chest pod! So overall a versatile piece of kit for £50.