Exhaust reducer

I’ve got an aftermarket exhaust that came with the standard 3 set reducer sleeves., the smallest being 35mm. My header pipes are 35mm too. My question is how damn tight do you have to tighten the clamp to get these reducers to work. I’ve got all 3 in (like Russian dolls) but it doesn’t seem to want to tighten. Any suggestions on what might work or I for it sounds as though I am doing something wrong.

Cheers

Exhaust reducer