We tried making the center Tetra by using only the clover leaves included with the kit. We wanted to see if we could save some time by not machining out the parts in the manual. Wow was that was flimsy
. So then we thought that aluminum might be stronger, so we rebuilt everything with the plastic clover leaves doubled up with a aluminum cloverleaf cutout. It helped a bit but not enough, so then we added aluminum braces and the thing was fine
.
But anyways... Aluminum is an excellent substitute, just make sure to round off the edges or duct tape them so they aren't too sharp