They would start to spin easier but would stop easier also. With the bricks in the end of the box, once it starts spinning it continues. Wayno
I learned this lesson the hard way. I built a "pump" trailer once for a firm that did water quality samples for perspective coal mines. They had to get water from numerous wells in the field that were anywhere from 50 feet to over 600 feet deep.
I used a flatbed trailer and mounted most of the running gear from a Ford Bronco on it. The 289 motor was in the front with the rear axle under it and I moved the front axle (this was from a 4X4) to the rear. There was a big drum I made in the middle that had over 400 feet of 2 inch hose on it. You could put different size submersible pumps on the hose and lower them into the well off the trailer. I drove the drum with a chain from one side of the front axle (welded the spider gears to lock that axle and also the other one). In the rear I drove a large Onan generator from one of the hubs. It could power a 5 hp submersible pump down in a well. From the other hub I powered a winch I made that I could run a bailing bucket down a 200-400 ft. well. In and out in less than a minute and I could bail about 3 gallons of water a minute using a 12 ft. long piece of PVC pipe with a trailer ball for a check valve in the bottom of it).
To power the drum and lower the pump into the well you put it in 4 wheel drive and un-locked the hubs in the rear and then only the front (use to be the rear axle) would turn and in 4 wheel low you could run the big drum real slow.
To power the generator you would put it in 2 wheel high and just lock the hub on the generator side. To run the winch you would do the same, but just lock the hub on the winch side. There was a big boom on top of the trailer that you raise and used with the bailing bucket.
Well anyway all of this machinery was mostly located at the ends of the trailer. If the trailer started to fishtail on the highway it was very hard to stop. Most of the towing was done under 60 mph.
I later made a second pump trailer and on this one I used a slant 6 motor and I made the trailer from scratch and all the components were near the center and ahead of the axle and this one did every thing the other one did, but had none of the bad behaviors the other one did on the highway.