The linear-loaded vertical doublet has been taken down, and the loading elements have been removed returning the vertical doublet to its original 20 meter configuration.  Now for the conversion to a twin-T capacitive loaded vertical doublet.
 
This conversion was much easier when compared to linear-loading the old antenna.  First, an eyehook was installed at the top of the vertical and the top-hat was installed.  To insure good electrical contact, a short jumper wire was run from the top-hat wires to a solder lug under the eyehook.  The top and bottom "T" sections were cut to 20 feet (10 feet each side) per Cebik's design.
 
(Updated 11/05/2012)
 
When I started to use an automatic "L" tuner with this antenna, I noticed that the tuner didn't like the impedance presented on the lower end of 40.  After modeling the antenna, I discovered that the resonant point wasn't in the 40 meter band, so I ran the model with different lengths of "T" sections.  30 foot "T" sections (15 feet per side), seemed to model much better, so I changed the wire lengths.  Now, the tuner is able to handle the antenna on 40 and 30 without any issues.  I use 100 feet of 300-ohm ladder-line, a 1:1 current choke, and 6 feet of coax to the shack.

I'm not really sure why my antenna was so different from Cebik's, but I suspect that the angles I used for the "T" sections caused the resonant point shift.  I suggest you model your configuration or simply start with 32 feet total length for the top and bottom "T" sections and trim from there.  This is much more important if your plan is to feed the antenna with 50 ohm coax.
 
If you look closely at the photograph above, you can see the small insulators on the top-hat.  You can also see the guy-rope lines and the feedline.
 
In the picture to the right, you can see the yagi, which is about 90 feet from the vertical.  You can also see the close proximity of the fence and in-ground basketball hoop.  I'm sure there is some interaction taking place.
 
Of course, the guys for the vertical doublet are made from rope.  I use 2 sets of three guy-ropes to keep the vertical stable.  The addition of the top-hat also helps stabilize this antenna.
 
The feedline runs to the second floor of the house, to the tower and down to a feedline junction box.

Here is a picture of the lower hat.  You can just see the black wires running up at an angle from the base of the vertical.  I know, you shouldn't have any obstacles around your vertical, but I'll live with this installation.
 
There you have it.  Nothing to it.
 
Please remember to review the original 20 meter vertical doublet (dipole) design for tube size and lengths.  You can also review the 40 meter linear-loaded modification to the original antenna.