Since I use a direct drive extruder, the x carriage belt was hitting the frame before anything else limiting the z below 100 mm. To avoid this, I installed the idler bearing inside the x idler end and designed a new belt clamp. This allowed me to go as high as 120 mm.The position of the hole for the bearing in the x idler end is off-center so that if you use a bearing guide, it will hit the frame. I used a spare threaded rod as a file to enlarge the hole.To apply tension to the belt, use a bulldog clamp to hold one end of the belt, while you apply tension with one hand on the other end and push the lock in with your other hand. Then screw the clamp on the x carriage.