Chris,
With all due respect for Jeremy, I had the same questions a little over two years ago. I had an '03 CRF450 that Jeremy did including Enzo subtanks. I loved the way things worked. But, as with any bike, once you get used to it, you start to notice things that can be better.
I noticed at a local track that I ride at a lot, in a long set of whoops with a steep faced jump at the end, that I would bottom out really hard on the face of that jump. I tried to correct it with adjustments, but had no luck. I started to turn in the adjuster screw on the subtanks to try and fix it. And, finally I got the bottoming problem fixed, I turned off the tanks. But, this led to a harsher ride everywhere else, so I kept going back and forth trying everything. I never got that problem figured out. I noticed the same little problems at a few other tracks, that had a landing followed by a sharp impact. It would seem to blow through what travel was left in the fork. If you have ever broke an air line on a subtank and had to finish the race with oil spraying everywhere. Then, you know what I mean, that feeling of not having an air spring.
Anyway, I got tired of drilling my fork caps too. So, I looked else where. I found a thread on another site talking about drilling or not. So, I did some research on the orifice sizes, and found Enzo's 3AN fittings, that screw into the forkcap have a 3mm I.D. hole. That is why they do not work well all the way open. Because, of the 3mm hole would restrict the CFM more than the valve. I saw a set of FVO tanks from Framebreaker Racing with a no drill system. I emailed them to ask them the same questions that you have asked, Chris. I even emailed Jeremy at MX Tech, and asked him some questions. What I learned was, the FVO no drill set-up has a 2.5mm hole as the smallest orifice size (The forkcap adapter). And, they use a different valve than Enzo with a by-pass circuit that allows a freer flow in return to the forks(Not a check valve). Jeremy told me that kind of system wouldn't work at all.(Keep in mind this was two years ago) But, I kept remembering some of the complaints that I had with the Enzo's, then I decided to give them a shot. Then, the guy's a Framebreaker Racing gave me a set plugs, that restored the forkcaps back to stock so I could try them on my '03 CRF450 and told me that they would give me my money back, if I didn't like them as much as the Enzo's. So, I got them and use the Enzo's back to back with the FVO system.
So, to keep the babbling down, If I were you, I would do more research. Don't just listen to the people selling the products, listen to what you want, and what you know you need, and listen to what others say that have tried them both. Jeremy, I still love your suspension and all of your help. But, I do love my newer set of subtanks too. When I rode with them back to back, I went to my local track to hit that section. The FVO system allowed me to have the valve open at a setting that I liked, (3.5 out of 8) and have plush forks on the entire track. But, I didn't bottom out after the whoops with the FVO's. I did go back a couple of times to make sure. The FVO's are different than the Enzo's, maybe it is the concept of a buffer as Jer put it? But, the quality is the same and I don't have any strange issues any more. I also like the fact that no one can see them unless they look really hard.(Hoses don't stick up) I have been racing for 15 years, and I know what I like and dislike. But, I'm just a local 200lb. "A" rider who loves to ride!
Like Jeremy said, "Be aware of cheap knock-offs trying to make a buck" But, just because it's new, doesn't mean it's cheap or a knock-off, it could be just improved or different. Does that make Honda a cheap knock-off of a Yamaha? Just because they are the original 4 stroke mxer? Different products work differently for some people. Some like Yamaha's I like Honda's, to each his own. So, don't be affraid to shop around and try new things.