for years now this is what I do.
1) take the first tarp, find the center. put a tall rubbermaid container underneath it in the center with the opening facing down.
2) take a second shorter reubbermain container and nest it on top of the tarp so you capture the tarp between the two nested rubbermaid containers.
3) position the assembly so that the rubbermaid containers are over the center of my 1350 TT.
4) take a much bigger (the white one, on its own would cover the entire trailer and all 4 sides of the tarp would almost hit the ground,) tarp, find its center, and position that center directly over the rubbermaid containers.
5) get some nesting 3/4" pvc electrical pipe, they clip together like lego pieces, and make at least 2 poles, one for each side, bigger than the trailer.
6) roll the excess tarp on pole like the tarp in toilet paper and the pole is the carboard center tube.
7) Home depot has for $1 4" wood spring clamps, the are like a cross between binder clips and clothespins, you'll need at least 8 of them
with 3 of the clips clip the wrapped tarp on the pole to keep it from unwraveling: you'll bind the entire pipe and cinch the tarp onto the pipe. do this on both ends and the middle, with the pipe ends sticking out on both sides. Repeat for the other side.
9) in the middle of the front and back roll the tarp up (you can even use more pipe if you like,) vertically, bringing both the sides in tighter toward the TT. use another clip to bind that.
10) in my area we are prone to 50MPH winds, so I will loop the end of the pipes that stick out with a bowline, the rope goes under the hitch (or bumper in the back,) and another bowline on the other side pipe. No need to make this tight.
the big thing here is its pretty airy underneath and most importantly the rubbermaid containers have made a center post, so the whole thing is shaped like an umbrella. As such the water/snow tends to run off instead of pooling.
The whole thing costs about $60 and lasts for years.