I would add, if you are using a robot, it will stay locked onto the prism when you set it down, as opposed to laying the rod on the ground. I usually key in whatever the next thing I'm going to stake before I ever pick it up.
Never had a problem with the TSC3 bracket moving. Maybe you're more delicate on clamping it to protect the pole? At the moment I've a steel pole but getting a fibreglass one to try and reduce the total weight of the pole. I never worry about over-tightening on the steel pole.
Yes why does the TSC3 need to be so heavy? Who knows what's in there...
I'm finding it difficult to get the rod rest at a sensible price here in the UK. (We only get a few pieces from the SECO catalogue in stock, everything else is shipped in).
So I think I'm going to have a go at making one. If anyone can tell me what the springs consist of I would be grateful. I am thinking that they are spring steel rods about 5-6mm diameter? I think the whole thing will me getting the spring force and the angles just right. I will have a bit of an experiment and see how I go.