Before I purchased a Butternut HF-9V vertical that is ground mounted, I had a homebrew multiband vertical in the same location. At one time I did feed it with open wire line, a few feet off the ground. I then used a 4:1 balun to change to coax just before it entered the house.
The antenna was around 30 feet high, but I also added some extra top hat wires to make it work better on 75 meters. It would have high angle radiation on the higher bands though even though I could tune it up most anyplace.
Although I am not a DXer, I was able to hear a fairly weak 75 meter KH6 phone station in the evening hours and was quite surprised that I was able to work them on the first call. I have never been able to do that with a low dipole from my QTH here in SW Wisconsin.
The advantage of using the Butternut is that it has a very clever design to use most of the antenna to advantage on a number of bands and allows you to operate on higher bands. With a 40 meter vertical, the radiation on 12 and 10 meters, and probably 15 meters, may not be optimum.