The missing tensioning mechanism is some heavy oversight in the original Mekerbot Industries design as is the original plastic belt that expands+warps due to temperature ('heated' conveyot belt *hint*) and wear, is slightly too short after purchase because it hasn't expanded yet and the completely missing bed-leveling mechanism.
Designing a shortened lever-arm for this one as the lower bolt is a bit higher due to my removable ABP mod.This allows me to quickly replace the belt with e.g. my PCB routing platform to mill electronics.
Have to start from scratch as there are no original design files for the tensioner are posted. Only an STL export and only as a complete bed of 4 parts.