Lou,
I have probably a similarly sized lot. Mine is 66 by 110, roughly. I have a
tree in the front that supports one end of the 75 meter inverted vee, and the
other is on a 20-foot mast at the back fence. The middle is supported on the
tower.
I've considered a quarter-wave sloper but haven't installed it yet.
Unfortunately, my tower is guyed, so there will be some interaction which will
affect the sloper's performance.
I'm guessing the reason you say you can't put up a regular antenna is the XYL
won't allow it to be supported in the front yard?