[Closed] Strap on bike racks and glass edged boots

Recently I changed my car to a new shape Vauxhall Astra and I'm hoping to use my old strap on bike rack but the edges of the boot are glass.

The rack has always had some strange black sausage looking things on the straps which, I've just discovered, are for wrapping inside and trapping in the boot so you don't hook anything on the edge of the glass.

I've got it to fit but I'm not totally convinced it's not going to break the glass and I can hardly keep up with the loan repayments as it is never mind a repair bill for the back window!

So, has anyone used one...? Was it okay...?

Cheers!

sL