Mmm... maybe too risky for me, and I don't have a decent vice anyway. But if it works for you, great.Probably not 100% safe but I bought some of these -
https://www.ebay.co.uk/itm/50x-0-5m...695409&hash=item2ce39e472d:g:nCkAAOSwZJBX~H1U
cut a can in half, put a bolt through the bottom, drilled four holes to fit the centrifuge tubes-just. Stuck the bolt in like a drill bit in my electric drill which I then put in my bench vice.
Ran it with a thick cardboard box over the top, it seemed to work reasonably well with no flyers yet!