Help me out here. There are LOTS of unistrt parts etc. What do you mean remove the other cross bars?
Sorry, I’ll try to clarify my thought.
There are 2 basic unistrut struts. One is 1-5/8” tall and the other IIRC is 3/4”. As far as I can tell, everything else is a variation or accessory on those 2. In most tents like you are showing, the aluminum channel you are asking about sits on another set of cross bars that sit on the longitudinal rails of the vehicle. The Unistrut is strong enough to span the longitudinal rails and act as cross bars while directly bolting to the tent bottom using the available strut system hardware.
Unfortunately I can’t find any pictures of the bottom of my Tepui with crossbars I made from the 1-5/8 strut and some little pads welded and drilled to allow easy bolting to the longitudinal rails of my Gobi rack.