Ok, forget the +6 slots, that might be too many. +4 would still have you having to make tough decisions when accessing. Krampus takes a long time to get to and I think the rarity of him should allow for a non-rare drop. I think common would be at 30% to 50% drop rate... increasing to the 50% the more times you've encountered him. Rare would be 3% to 5%... increasing to the 5% the more times you've encountered him. By the time you've possibly encountered Krampus and get a sack, you've probably already have multiple bases and transporting stuff isn't that critical.