Butternut HF-2V 160 Mods.
There isn't a lot of science behind the Mod. I read about the higher efficiency and greater bandwidth of short verticals by moving as much of the loading as high as possible as well as adding as much capacity hat as possible. I didn't try any other changes (larger coil) as mentioned in the Mods.
My experience was that the bandwidth was wider and that I was able to break pile-ups that I simple couldn't before (had to wait until there where no other callers and then I'd sometimes get through).
I've worked DXCC on 160 with this antenna (and 750 watts), the first 50 or so with the stock antenna (with the 160 kit) and the rest with the modification as shown here. The last 50 where a lot easier.
Any questions are welcome at firstname.lastname@example.org.
Also, I recently installed a BiggIR and HF-2V side by side with no degradation 160 and 80 meter performance.
Since these slides where made, I've mad further changes to the HF-2. I extended it by 4 feet and removed the 80 meter loading section. I left the 40 meter loading section in order to tune the HF-2 to the 80 meter CW band segment.
VE6LB home page (click on the picture): http://www.ve6lb.ve6hams.com. For details, drop me an email.