I made a bed leveling probe out of the hotend itself. Per an idea by Daniel on the deltabot forums. The resulting design is much less bulky than the original. The key features are: no deploy/retract required, no pin/spring/collar required, no bulky tower to hold pin assembly. The requirement for use is to perform a pre-heat and wipe of the tip to clean it before probing. This can be done via start-gcode commands prior to issuing the G29 command to auto-level.