GT3541L with a Markins base TB-30 and a Arca-Swiss Monoball Z1 sp "Flip-Lock" For bracket I have a RRS D3 L-bracket, BD3-L.
The Markins base sits perfect on the Gitzo and the Z1 monoball looks married to the base. The RRS brackets is the only bracket I have so far so I cant speak for how much it differs from others Arca-style brackets. The RRS is rock solid in the Z1 flip-lock and setting up the Z1 according to instructions was easy to do though the flip-lock could have been a little easier to handle. It take a few tries to get used to it.