I made an interesting "discovery" yesterday afternoon.
A while back I found and ordered an S mount to Elinchrom mount adapter on eBay. I ordered one and when it arrived spent a couple frustrating hours trying to mount the Elinchrom ring onto the front of a Cheetah Speed Pro Bracket. That didn't work and I kind of forgot about the adapter.
Then yesterday I had a thought how would the Cheetah Light work with the adapter mounted on the Speed Pro Bracket. So I gave it a try. First I mounted the adapter, then mounted the light and slide it into the throat until the locking screw hit the upright. The result was less than satisfactory;
Here's another angle that shows the position of the light on the bracket.
Then I had a thought, how can I get the knob past the upright? The answer is to not mount the light on the bracket before wiggling the head through the upright. That worked like a charm. Then mounted the light on the bracket. Finally I fitted the S to E adapter. It snapped into place without a problem.
Here is the result;
and a second view;
The final result is the flash tube being well positioned in the modifier when its mounted on the E mount.
Also, just a reminder, the E mount on the adapter is a really cheap plastic item that may or may not be durable. At least its a solution until I find something better.

When I get a chance I'm going to mount my Fotodiox EZ-Pro 30" octa. Its a nice deep box similar to the Elinchrom Deep Octa.