I also live in a city lot and my tree was only about 35' high. I had very
good luck on 160 M using an inverted L, a 1/4 inverted L.
Fed at the base. You might try something like a 1/4 inverted L for 80 meters.
Get the vertical section as high as you can and then take the horizontal
section to another tree. Mine went over my roof to the front yard tree, not
much hight then 35' either. It worked very well on 80m.
You could try this on 40M as well. If you have no other support for the
horizontal other end, then you could even slope the horizontal end down to a
fence.
Also look into 3/8 or 5/8 wave inverted L. They work even better.
My inverted L, was wire up the tree and over to the front yard tree. Fed at
the base of the vertical section of the wire.
The more radials the better.
73
Craig N0BSA