Adding the 2nd tower doesn’t do very much for stability, unless you add bearing extensions to the bars of the bottom linkage. With 2 bars, the screw has to be fixed to the tower, whereas the screw can be fixed to the linkage if it’s cantilevered. Thus, you can rotate the c-channel sideways or ad a c-channel coupler to the other side of the tower to provide 2 points of contact with the screw, as opposed to just one with the 2 bar tower (unless you use bearing extensions). Furthermore, using 2 bars means you have to counter the torsion of an extra c-channel to maintain stability, which is harder than bracing just one. If you have the space to build a sturdy 2 bar tower, it could be better than cantilevering the joints, but especially in this game, you likely won’t have the space, and it’s much easier to cantilever them. You can learn more about this in the DR4B Tutorial by 333A.