Shapeoko 3 z axis belt tightness?

I have just bought a Shapeopo 3 and this is my very first CNC build. Well I have followed the build manual but now compared with the X and Y belts which are nice and tight the Z belts is oh so slack. Starting at the motor one side comes down to the bottom guide it then comes back up to the two guides and round the fixed gear but the belt is still very slack.

There should be some sort of adjustment mechanism. On my original version SO3 I had to use a small pry bar:

I did a jury rig to tighten mine, but it worked. I glued two pieces of wood onto the sides of the fixed gear, so that as the belt wound around the gear, it had to go further, which took up the slack. The pieces were glued on the top and bottom of the gear, respectively, which left the “far left” side gear cogs able to still engage the belt, keeping it from slipping. Alternatively, you can get a replacement gear with more teeth, which is a cleaner solution. Lots of people have the same problem, so I’m sure there are a bunch of solutions. Seems like a design change is in order. Good luck!

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