I can tell you that these PTO driven spreaders have the capability to really throw the material in a wide area. I couldn't get mine to throw granular fertilizer less than 30 feet wide no matter how slow and reasonably low to the ground I ran it. Running it at the PTO settings on the tach, holy cow, I bet it threw fertilizer 65 feet + wide from side to side.
I tested it in my 35' wide streets to see how much material it threw. I also measured it in the cul de sac, which is nearly 100 feet in diameter. Granted, granular fertilizer is going to roll some on pavement, but even on the lawn it was at least 30 feet wide at the lowest and slowest settings. I was overlapping far too much when I had the spreader set at the suggested material flow rates.
With my prior pull behind spreader with 300lb capacity, which was broadcast with the spreading spin being driven by the rotation of the spreader wheels, I could cover a width in the lawn of about 15' to 18'. I overlapped accordingly. The 3 point PTO driven spreader is a whole different animal in spreading width, spreading material volume and loaded material capacity.
Keeping the snow and moisture off the sand in the hopper is going to be key to a good material flow. The hopper is going to have to be covered whenever outside. I have no doubt it can spread sand, but I would expect the moisture to wreak havoc on causing clumping, etc. as well as inconsistency.
If you have a cab or enclosure on your tractor, you will find opening and closing the spreaders control valve a challenge as it's hard to reach with a cab or enclosure on the tractor and will likely require you to get off, open the spreader, get in the cab, turn on the spreader and then, you have a blast of heavy material for the time the spreader is flowing before it is spinning.
The density of sand and it's weight are going to make for an excellent rear ballast / counter balance. It won't take long to have 500 pounds of sand in the hopper. Even the small 3 point PTO spreader would be very heavy were it to be filled with sand.
I would also suggest if you use a 3 point spreader for sand, put very little in the hopper while you are determining spreader widths and volumes, maybe start with 30 to 50 pounds. Because if the spreader does clog or have issues, removing the material is a pain, so you want the least amount in the hopper to permit you to see if the spreader is doing what you want it to.
I plow a lot of driveways (17 this season right now) and at least 3 of those require regular snow melt application of material. I found that for my needs, the spreader just provides way too much material and throws it well beyond the driveway width. I choose to use a hand held electric spreader and with the snow melt I am using, a little goes a long ways.
I can cover most 100 feet long driveways and the parking area as well as the front home entrance steps, etc. with less than 6 pounds of snow melt product. Using that amount, I am able to keep the surfaces clear of all snow and ice other than during the worst snowfall conditions.