This post might be of interest:
As @dlang said, first you balance the sled, then adjust the motor mounts to keep the chains parallel to the sheet.
Ways to balance in order of how much the impact is on the sled tilt:
- hight of the mounting for your triangular kit
- weight below the router
- with the top mount kit you can mount the arms the chains attach to, either on top or down and with washers (spacers) you can fine tune in both directions.
My example for the approach (likely not the best way to do it):
Fist was A, a rock solid hardwood with screws, dowels and glue.
Screw and dowel holes in the sled an through the hardwood drilled with the same g-code on my desktop-cnc.
Second I used ‘wheels’ leftover from a lighting project to stack until I thought I have the height.
With this measurement I cut block B and again used the cnc to drill dowel and screw holes so it would fit on A. Maintaining the correct distance to the bit is crucial.
I ended up to high 
so until I find a way to bring B down evenly, I mounted the ‘chain-armes’ from down and added bearings as spacers to lower more.