What happens to the performance when a HF dipole installation is raised?

I was sort-of satisfied with my folded dipole for 17m and 20m bands, when it was up about 10 meters. Still I wanted to optimize it...I am a radio amateur, right? After a couple of hours of sweaty climbing and wire tinkering I found myself looking at a dipole that is horizontally at almost 20 meters up, the wires pointing roughly to north-west and south-east. I don't know, if that's a good direction...I don't need directivity gains especially, since I work all the world and at random times, but let's try the antenna now! Well, I need a shower first...

The folded dipole for 14MHz and 18MHz is now almost 20m up. (Click for bigger picture)

Zoomed picture of the dipole up in the sky. The spacing between the lines is 30cm (not cricital) and  the  RG-58 cable  connects to  a 4:1 balun.

The VOACAP propagation forecasting tool showed interesting changes in the antenna performance:

A sample VOACAP propagation forecast for 11.May 2011 16 UTC for a 14,1 MHz QSO where my the dipole at the other end is 10 m up and my dipole is 10m up.

...and here is how the forecast is affected by moving the dipole to a height of 20m.

And what is the real life?
It was late afternoon, when I swithed on the radio, eagerly waiting for the results. I know from theory, that this height is really good for 17m and 20m bands...my little concern was: do I get DX QSOs on east and west directions with this installation?

When I sat down in my shack I decided to start calling CQ with PSK125 on 14 MHz. BD1MWH from China responded at once...not bad! Soon I had PSK and RTTY QSOs with ham fellows in South Korea, Philippines, South Africa...and later in the evening also Brazil and Bolivia on CW. Three new DXCC countries in the same day!

How is this with Eznec?

Elevation diagram for my horizontal dipole.
The lower lobe is at an angle of 13 degrees and the higher is at 45 degrees

The azimuth diagram for the 13 degree lobe. Good DX possibilities in two directions.

The azimuth diagram for the 45 degree lobe. Directivity is not that much of an issue,
which together with the high elevation angle enables good QSOs in Europe.

Antenna pictures

After a few months of active ham life :) I have now three antennas in my garden:

• Windom for 80-10 meters. Nice DX contacts made on the 15 meter band.
• G5RV for 80-10 meters (does not work really well yet...investigating)
• Folded dipole for 20 meters. Installed 10 meters up. Works quite well also on the 17 meter band.

Here are some pictures of my little antenna park. Pictures taken in february 2011. The windom antenna is not very obvious in the pictures: