I tried glass and eventually added a 3 mm aluminium plate on top of the existing one.
used kapton tape to secure at the corners. And haven't looked back since.

I can pretty much guarentee if I'd had a glass plate it would have broken by now.

Some of the prints have been brutal to remove. Cracked it now, for the relectant prints I just heat the plate up to 60 and I can get my scraper under a corner.

Find a local aluminium engineering firm and get tham to cut a piece of scrap to size for you. It'll be cheap.

Also for an extra 3mm you don't need a shim.
There should be more than 3mm play in the adjustment springs, so you still get full build height and don't need to fiddle with anything else.