Just wanted to provide some information for people like me that had some question about the Downshifter.
First I have to say that Rich's service is stellar. He was a way for a while, but still answered all my emails in a reasonable time. The when he returned home he shipped it immediately and it arrived much faster then I expected. Thank you so much.
The Downshifter is easy to install. Remove the lower E fine tuner and remove the small washer (be careful not to lose it). Install the small washer on the bottom of the new Downshifter (may not be neccessary but it will keep it safe) screw and thread the Downshifter assembly into where you removed the fine tuner. Tune the guitar. Done. It is not tricky, it is that simple.
You can use the new barrel to tune the guitar (like a fine tuner) you do not need a screw drive to turn the screw the barrel holds the screw in place. Basically the barrel is notched so that the screw will either ride high or low in the barrel depending on the screws orientation (see photos). So turning the barrel turns the screw.
Operation? OK. The barrel make it easy to tune the string, IMO easier then the normal fine tuner. Changing to Drop D does require tuning adjustments. With the ZPS the other strings will stay pretty close or maybe perfectly in tune. The low E, now D will need to be tuned. This also means you will need to tune when you go out of drop d. It does not have a set screw like the D-tuna to fine tune the drop tuning. This a great feature of the D-tuna, when setup right it drops perfectly, everytime. To change from E to D or D to E you either press down on the barrel or the saddle and turn 1/4 turn to allow the Dowshifter screw to be locate in the higher or lower spot of the barrel. It is a very, very basic device.
It work goods given its design and I do not really notice it is there when playing. IT looks Ok, but not nearly as sleek as the normal tuner. I think that Rich's clunky comment is more about its how you change to drop.
Now, I installed this on a 2011 model ZR. I have noticed two things; my E fine tuner removes easily compared to the others and it appears to have a much longer thread. I can go from E to D using the fine tuner and I have plenty of adjustment left (not a ton, but enough).
I would recommend the Downshifter if you can not get to drop D or you just need more tuning room. It functions fine, but it is not a D-tuna.
Downshifter Barrel and screw. Notice the groove inside the barrel, this is where the screw slides in to drop the tuning.
Downshifter screw, note the tabs that slide in the barrel
Normal fine tuner and assembled Downshifter.