Jeff,

A disclaimer... I'm not very experienced at hardware.

First thought was the wire arrays you mentioned. Sounds like you have that ability. Seem to recall an ARRL compendium article, or maybe it was in QST, about a guy who built a 15 mtr beam he hauled up and down. Something like that? Rick might give you some advice on stringing a low band log periodic between two trees   ;-)  Those tips might apply to using a line to support other types of arrays. Doing a delta loop beam would probably play well at 65 ft for 40 and up.

Secondly, if I couldn't do a tower and had your space I'd probably take a close look at a steerable elevated vertical array. I liked the data and advice N6LF gave about using more than 4 elevated radials and putting them higher than normally thought of as needed. He said doing that adds a dB or two and minimizes external influences. Can't do much about far field loss though. I've kicked the idea around of trying a bob tail. My property line runs broadside to EU.

It ain't much gain, but some here in SC have jumped on the Super Loop band wagon. They are happy, but I can't help but think what you have now is just as good or better.

Kevan N4XL