My 5-ton military truck has an oscillating 5th wheel plate. There are blocks that can be put in to lock the sideways movement if needed. Should it always be blocked except in rough off-road conditions? Would you give up some stability if you let it rock free running on the road? I'm still in the process of finishing up the trailer and haven't hauled the D6 yet.
It should be more stable with the 5th wheel locked. Leave it locked most of the time. I"m sure there something in the manuals about when to unlock it.
I would be inclined to leave it unlocked if the load is balanced well. The blocks hold it while loading and unloading especially when loading heavy to help stabilize the trailer. There is less side stress on the pin and the trailer plate always stays flat on the fifth wheel when traveling with it unlocked. The militarys intention was to keep the fifth wheel connection from extra stress in sever offroad twisting conditions. That being said there are millions of trucks on the hiway that do not have side tilt so you don't have to worry either way unless you are going rock crawling with it.
This is our set up with the more conventional 5th wheel arrangement. We actually made up & installed these blocks to better match the trailer gooseneck/ tractor heights. I think by leaving the side to side rotation locked, it may be better, affording better stability when loading. As OIH said, there are millions on the road, set up that way. In your case, if you have are travelling over rough "off road" terrain, you have the option of removing the blocks.
I'll likely leave them locked. When I got the truck it looked like the locks had never been moved. I suppose my other option would be to change the 5th wheel to one that's lower height. On these trucks the plate is about 10-12" higher than a commercial truck....that would get trailer a little closer to level.
I've fab'd ramps-5th wheels for a few new KW-Pete Cali style, you can get different 5th wheel base heights. If you're on a narrow twisting curving trail and the trailer wheels hang off the dirt road the rocker 5th will help dump the machine off the side, LOL
I would block the oscillating feature up tight & forget about it . My opinion is the oscillating 5th wheel was overthought to begin with & not needed for hauling heavy equipment like a dozer . They forgot the low boy trailer frame will twist around on uneven ground . I wouldn't loose sleep over it . Have same issue on 5th wheel on the KW , it sets about 12" higher then a standard tractor . We ended up modifying the gooseneck on the lowboy so it would set about level . Then when I hook to it the old 74 Pete with low profile 5th wheel it sets a little low in the front but still works fine . Hey , keep it under 13 foot six inch and as long as lowboy don't belly out on a high rail road crossing we call it good bro :thumbsup