On the part you took a picture of, roller f, the longest bolt controls the tension. Make sure that is very loose. Then tighten the the 3 bearings. When that is done, only tighten the longest bolt enough so that the motor mount is not flopping in the wind, but still loose. The zinc coating will wear off very quickly after an hour or so of use and allow more room. All of this has to be accounted for initially or the machine would be sloppy.
That middle bolt, plastic on both sides, is on all parts and is the only one you need to make sure is loose.
The goal of all the parts is to flex them to get them to edge of there plastic deflection to minimize flex when in use, flex by design to pre-load them or they will be springy and loose after your break in. You are using my parts, that I printed, on the exact same conduit I use. You should be fine. I admit the corner blocks are too tight but they work fine, They have to be this way because of peoples poorly calibrated printers. In the beginning there were complaints of them being too loose. If I was printing all parts they would all fit perfect.