Used luc_e's wonderful tripod arms but needed to attach to existing tripod.
I used 2 of the tripod_top pieces. The one at the tripod I tapped with 1/4 20NC threads to screw on the tripod. The other used normally at the camera.
This connector ties it together with as many arms as you like.
Edit: To make this work better could glue and press in one of these 1/4-20 inserts vs tapping plastic. Mine is already coming loose.