Hi Robert
I used to use a stooge for my stunters on the grass patch we flew from; easy to make...
No pictures I'm afraid (it's long since passed to a new owner).

A block of hardwood (mine was @ 2 x 1 x 10") with 2 holes drilled through the face to allow it to be staked into the ground with a pair of tent pegs.
On one side (the 1" edge) attach a wire arm (14/16swg) with an 'L' on the end that is a
loose fit into a hole in the block (screw at the other end) and a kink about 1/2 way along.
Fix a length of line/string to the kink longer than the lines you use. When you pull the string the 'L' pulls out of the hole

Now all you need is to solder a wire loop to the tailwheel of your stunter.
To use - first lay out the stooge and line. Then locate the 'L' in the wire loop and check it's secure. Start the engine and walk to the centre of the circle. Pick up the handle first then a tug on the string will release the model...
Phew - takes longer to describe than make.

Don't use a string with a lot of stretch

I had no problems over several years and used it with every wheeled CL model I had. Light and easy to chuck in the box with the other bits and bobs
Have fun
Paul