Kerf bending a square tube

Hi

I am looking to get some steel square tubing bent using a kerf bending method by laser cutting out sections (see image for example)

I have a manufacturer that can do it  but they need to know exactly how much to material to cut out. I have tried simulating this in soidworks to find out and using the flex tool I have managed to get the bend I require. The issue is the cut outs don't seem to be reacting correctly, I would of though a bend at this radius the cuts should touch at the ends but they don't (see image).

I need some help getting the material to simulate the bend correctly so I know how much material to cut out.

Thanks

Jack