My barrel is sleeved but thick flange and large fin and on standard bore of 70mm nominal, the sleeve has a wall of around 1.5 maybe 1.6mm and accepted wisdom seems to be you can bore them down to a wall of 1mm thick.
So accepted wisdom is to bore my barrel's seleeves to 71mm or plus 040 "maximum".
I don't think I would go beyond plus 020 but hopefully I will never have to make that decision!
Theres quite a few posts on sleeves on this forum but i hope that helps