I have a 12x6 10k dump trailer that I absolutely love. However, I will say that I wouldn't even consider towing it with a 1/2 ton and a load of gravel. I have a 3/4 ton diesel and looking at my last ticket load of 5/8"-0, I was hauling 3.5 tons which put me about ~300 pounds over weight actually (trailer is around 3300). I can tell you that you most certainly need the additional power if you are going to pull across any grades, but as mentioned a number of times, even more important is your ability to stop this much weight. I have a brake controller, but I know people that tow the same size trailer without one and to me that is just a huge accident waiting to happen. Why take the risk? Cost me around $100 for the brake controller and adapter and took less than 5 minutes to connect and mount it.
BTW, even with my trailer, it isn't cost effective for me to haul any sizable amount of gravel. I usually order it in 30 ton increments from the rock pit. The distance is about 20 miles over backroads. So, for me to get 3.5 ton of rock in my trailer, it costs me about 5 gallons of diesel, so at $2.50/G right now, that is an additional $12.50 each run, not counting my time or vehicle and trailer wear and tear. So, for me to do the equivalent of 30 tons, it would take me around 9 trips, so an additional $112.50. It costs me about $200 for delivery for all 30 ton in a single delivery and doesn't cost me a cent in maintenance or time, so in the end it is absolutely cheaper to have it hauled.
Now, that said, I love my trailer and use it for a lot of different things, from hauling bark dust, to moving my tractor, to you name it. So, I would definitely recommend a trailer if you can get one, just don't expect to haul heavy things in it with a 1/2 ton, and no matter what, get a brake controller.
