Presently I'm converging on figuring out what my "big" antenna is going to be. After visiting Bill, W6WEM and seeing his 80m loop I think a skywire loop is how I'm going to go. Bill uses 450 ohm ladder line and a transmatch on his antenna. The area the antenna covers is less than I'd anticipated, 80m isn't too much when divided four ways.
I'm still undecided about whether I'll make an 80m or 160m loop--that depends on measurements of possible support locations. I'm going to start out trying a coax feedline with a Q section as described by WA4HWN.
That saves me the cost of a balun to hook up the ladder line to my rig, for now at least. Eventually I'll probably end up with one of the manual tuners with a balun in it, but for now I'll plan to try the coax method for this antenna.
For supports, I have some trees but I think I've got an idea for adding some masts in the right locations if they become necessary to get a fairly round or square shape relative to a couple of trees that'll get one side up about 40-60 feet above the edge of a ridge at one side of my property. The antenna may end up sloping down a bit from that height, but less than the ground's slope and likely less than 20' of slope from one side to the other. Not quite as horizontal as could be, but adjusting just how high I put the supports on the high side could flatten things.
Any comments on my ideas are appreciated, this is the point where it's still cheap and easy to change plans. I'm particularly interested in comments on the feedline particulars and the height/slope of the antenna. Anything else is open for comment, too.