Just to clarify, Bruce and Ultpanzi are talking about 'conversion' necks not standard baritone necks. These are designed to be a straight swap for a regular scale guitar and have their fret positions calculated accordingly.
I get what they are doing. It has to be a whole new neck. The basic premise being that they have added two frets from the NUT.
Here are the scale lengths for the two guitars Warmouth mention.