Try this. Assy the way you did just snug and put a feeler gauge into the space between the hub and wheel. Measure at four places to get and average. File a little bit less than the average that you measured with the feeler gauge off of the spacer. The problem most people have is they dont have a way to measure the 7 plus inches. Go slow. If you dont take enough the hubs will preload and if you take too much the axle torque will do the same. I think that the multiple hub bolts would put a lot of side load on the bearings. Let me know how it goes.
Unfortunately, I have already assembled the hubs to the wheel using red loctite, as a side note I attempted to use loctite 37700, a paste, with the primer, and found it set up too fast and altered the torque, I had to start over, after cleaning everything again, and then using the more traditional red 263 loctite with primer (which worked well and gave me time to torque the bolts in two increments).
I would really to know if others have had the same issues with the bearings tightening up to the degree I explained after assembly of the hubs to the wheel. Not knowing what the factory tolerances are/were I would have no idea how much material should be removed, if any, to ensure the bearings have the right amount of preload. Once that material is removed it would require a new bearing spacer to be created. I was able to measure the length of the tube exactly as I had an extra-long dial caliper. I see the bearing tubes being sold for K9's and 2007 and later Mastiff's but none for the 06 Mastiff. I would really like to know what other's bearing spacers have measured, again mine measured out 7.2010" length, 1.0035 I.D. and 1.2535 O.D. I hope someone else has measured their 06 Mastiff's rear bearing spacer.
Olde Man I appreciate your suggestion and I should have thought to measure the standoff measurement before applying any torque to the hub bolts but even then, it would have been a guess as to how much material to remove from the tube.
