If people can crane massive panes of glass across building sites using suction cups, they should be ok for a camera.
I'm probably gonna use 3 cups to be safe though. 2 cups are strong enough to hold the rig with camera on it, but if I have 3 it means that should 1 let go, there's still enough to hold it.
Been doing some checking and all the flex I'm getting is from the center section of my boom which is because it's thinner so that I could slide it inside the other 2 sections. Gonna get some thicker stuff tomorrow!