Martin,

The tripod is steady, even when extended. The
wood part is attached to the tripod only at one
location. That is what is a bit wobbly.

I tried it out indoors with a double rifle and
it seemed to settle down alright. When I test
it at the range, I'll know for sure.

Dave,

Your method is fine for the front, but I also wanted
some support for the elbow of my shooting hand. Sort of
like how someone bends down, holds on to shooting sticks
and you rest that elbow on their back/shoulder.