Re: slalom off tower
My guess is that a properly installed tower would handle the the strain of slalom. The question would be why, though. A wakeboard tower promotes different ski movement patterns.
You can see what I mean be watching a really good slalom skier. You will notice they engage the entire ski edge as they cut and at the same time their upper body (and ski rope) approaches being low and parallel to the surface of the water. With a tower, the rope will angle up, which forces your balance more aft. The slalom cut will be using just the fin instead of the entire ski edge.
That's my $0.02.