[AtomicLabMonkey]

The purple strap stays on the lower bar because you weld or thread a retaining washer/nut onto the front end of the bar. And if the net assembly is installed correctly it will be under some vertical tension when you have the top spring loaded bar in place, so that lower front corner won't move much laterally. Yes, it will of course deflect a bit if something impacts it, but the function of the net these days is basically only to keep your arms inside the vehicle, and it should do that job fine. It doesn't have to take the force of a full torso hitting it like in the bad old days when guys raced on bench seats with lap belts & jockey helmets.