There are many instances in Pathfinder and other 3.5 based systems when you might need to reduce a monster below 1 or 1/2. For example, if I'm using a CR 1/2 monster from a 3.5 source in Pathfinder, I'm supposed to reduce it's CR by 1. So what do I do in this case? Reducing the CR by 1 using rote math would put me in negative territory. Or, for a more practical example, what if I want to include many weaker versions of a weak CR 1 enemy? I'd apply the CR -1 template, but then what would the CR be?
Do I drop down to the next fractional CR? Or do I go in halve the CR?
Note: I realize that this is partially a theorycraft question, since this situation only occurs at very low level encounters or in encounters with LOTS of low level enemies. However, it's been bugging me for awhile and I'd appreciate your input.