One source described part of the design philosophy for CMP trucks as being "use one size heavier than normal practice". I.E. use higher capacity (but still off the shelf) parts than might be expected for the carrying capacity of the truck to allow for the "abusive" loading and operation the Army subjected their trucks to. Other sources have described the Maple Leaf trucks as being "Heavy Duty Chevrolets made in Canada". I'm not saying these statements are 100% accurate but they might explain the disagreement seen in the posts above concerning component sizing.
On the topic of split rims - they can be perfectly safe if in good shape and treated with respect. Worn, rusted, mismatched (rim to ring) or otherwise abused wheels won't properly engage and may separate as they are being inflated. So yes, a cage or other restraint is very strongly suggested for safety. The real nasty split rims are the Firestone (and others?) RH-5 rims produced long ago that separated near the center of the rim (as opposed to at one side), have less bearing area along the joint and can't be visually inspected for engagement. A group of reference charts on servicing one piece and multi-piece rims can be found at
http://www.kentool.com/index.php/new...safety-posters The content originates in the USA but should be basically the same worldwide.
This link from a rim manufacturer describes safe tire mounting processes
http://www.accuridecorp.com/files/20...4-06-22-12.pdf It specifically describes treatment of multi piece rims. If these rims had been banned for safety reasons I strongly doubt that a manufacturer would want to get into the liability arena of describing how to use an outlawed product. The document has a 2012 copyright so isn't badly outdated - nothing like our beloved MB-C2 or MB-F1 that were published 70+ years ago. The publication also refers to a multi piece rim for tubeless applications. I hadn't realized they existed, thinking the joint in the rim would let air escape. Apparently the inner edge of the bead seals on the main part of the rim and the side/lock rings are narrow enough they don't interfere with the seal.