I checked it this morning & after releasing the clamp it certainly didn't spring back as far as it's original position.
I'll give it a while longer & if necessary, I'll pack the ends to be a bit higher off the bench so I can put more pressure in the centre.
Thanks for the tip about the rearmost bar - I'll check that carefully when I get to that stage.
What strengthening did you put in your roof (if any)?
I'm obviously going to have to fit a raised lip all the way round but just wondering if more is needed.
Could you tell me the dimensions of the hole in the roof?
Also, my front bar fixings are 75cm apart - does that match yours?
My plan is to cut the hole undersize, mount the front bar & then open up the aperture so the front bar drops neatly inside the hole. Then I can weld in a lip.
Thanks