Alloy profile rig question

[hazardpro]

So apart from owning a P1 rig I have no experience with alloy profile stuff....

I’m making up a seat belt tensioner system (thanks Chris Green)...

But I don’t want to mount it to the back of my seat (various reasons) so want to make up a frame to mount it and the motor using 40/40 and 40/80.

What I’m not sure about is it’s rigidity vs my “design”.

I’m happy with the design but what I don’t want is it flapping about on my motion rig.

I appreciate it’s a bit suck it and see but can anyone with ‘making it as you go’ experience take a look for me. The uprights are 1m tall and it will stick out by 330mm to give you some idea of scale

Here is my very shoddy drawing

Note I have a motion rod so it won’t be sitting on the floor... it will be suspended off the back of the rig thanks