Tires for the '07?

I've replaced the tires on my new '07, wanting to upgrade from the stock "P" rubber to "LT" load range tires for the towing I do. I found a somewhat limited selection in the 275/65-18 stock tire size; I ended up with Toyo Open Country ATs, which I've had on my Gen 1 tundra and have found to be excellent tires. But, I had to go with 10 ply (load range E), which seems like overkill,, as the supposedly available 6-ply version of this tire could not be acquired by my local dealer. (I'm in a rural area, where my local selection is quite limited.)

I now have a balance problem ( a little, but very annoying, wheel wobble at around 55-65).:td: My question is whether anyone thinks that these 10-ply monsters are too heavy for the truck, or is this balance problem solvable? The tires have a thirty day return privilege, so if I can't solve this pretty quick, I might just go back to stock "P" load range tires.

Any advice is very much appreciated.