Amateur Radio CQ WW RTTY contest 9/22-9/23/17: 40m contacts using an end fed wire antenna at 5ft

I worked a few hours in the CQ WW RTTY contest today and logged 30 contacts so far, mostly on 20m, a few on 15m, and then this evening several on 40m.

For 20m and 15m I have homebrew wire dipoles in my attic at about 33ft above ground. They probably don’t work as well as they would at the same height outside in the clear, but I logged contacts (from Davis, CA – grid CM98dn) with Japan, Mexico, Chile, Uruguay, Hawaii, British Columbia, and across the US. I’ve worked my Worked All States (WAS) with these antennas, they’ve been working well for me so far.

I haven’t worked out a 40m dipole that will fit in my attic (without some serious bending back and forth), so for 40m and 80m I have a Maple Leaf 160-6m 60ft end fed, which runs along my backyard fence line. Now at about 5ft above ground a 40m antenna is far below it’s optimal height above ground (at least for a 40m dipole which should be 66ft above ground), and yet this antenna works. Does it work well? Probably not as well as an equivalent 40m dipole up at 66ft, but using this antenna this evening to work some RTTY contacts on 40m, I made 6 contacts all between 500 to 600 miles out to the East and South, and then one slightly further out, up to BC at about 700 miles.

I think at 5ft above ground this antenna probably qualifies as an NVIS antenna, but working contacts out to 700 miles is ok for what I’d consider a compromise antenna, or at least with a compromised installation. Or am I misunderstanding how these end feds work?