chainline - using gxp bb spacers

have issues with my chainline. its single speed, and i want the freewheel to sit further out to be inline with chainring. To do this I have some spare spacers that came with my sram gxp cranks. They fit perfectly over the threaded hub. They are made of plastic though, admittedly it is a very hard plastic, I am worried when I apply force the freewheel could potentially tighten more and crush the spacer or at least deform it. Thats my theory anyway. They sell aluminium 6061 spacers on ebay for this kind of job but charge £11....Anybody attempted this?

Cassette spacers on plenty of cassettes are plastic....

Cassette spacers on plenty of cassettes are plastic....

The gaps in a cassette aren't under much compression though.

@user71349 you're right, as you pedal the freewheel will tighten and compress the spacer, I'd be worried about using a plastic one too.

I don't think you need to pay £11 for a metal spacer though.

Here's a steel one for £1.91 delivered.

The gaps in a cassette aren't under much compression though.

Go on, how so? Would've thought they'd be the same?

I have cracked a BB spacer (Shimano) once on my MTB by (presumably) tightening the BB cup up too much though.

Ignore that, thought the OP was using a normal freehub instead of a threaded one.

Thanks for link, ordered a few last night though. Cheers.