22 days ago - Rokvach - Direct link
We took extra steps to make sure that this doesn't happen, if you launch a older save where the toolbelt used to be 12 slots it will now spawn in a bodybag next to your character with the excess items from your toolbelt in it.

Only issue I have so far noticed about older saves is that some items doesn't have their stack restrictions, for example you are able to stack 8 oxygen tanks in to a diving mask, this shouldn't happen but seems to happen in older saves.