"Now here is the kicker. I was cleaning up and I picked up the one plastic HL tan sprocket that I used to help adjust and eyeball measurements and put it back in the HL accessory bag that they included in my kit, (I used metal sprockets) The bag contains the sprockets, HL size sprocket screws, spare plastic track links, and....... two white plastic thingies. I noticed them and pondered their importance. I pulled one out and it was delrin or something similar, and its D shaped, like the axle shaft. I measured it and it is 4.5mm long. It hit me that DKLM included this as a spacer to go inside the sprocket to push it far enough out from the tank to run. The bad thing about doing the spacing this way, one its only 4.5mm and I believe it takes 6mm additional to get a correct alignment, and the other is you take up all the space in the sprocket and are left with very little to hold onto the shaft with. If the track binds or throws your likely to twist that plastic sprocket right off the shaft mounting tube. Any way so there is that mystery solved."
Sounds to me like our manufacturer planned more on a static model or at most a wood floor runner. Still and all, you are doing a great job on this thing!