What extensions are compatible with the UCM brackets?

[MoverMarcus]

I recently got the UCM strongholds for my gladiator NXT's

Currently I am considering putting extensions on the UCM brackets, but I am not sure what is compatible. For example I am considering putting a tablet and/or streamdeck XL on the brackets. Does anyone have put a streamdeck succesfully on an UCM bracket and if so how did you do it?