Scott, let me preface this by saying that, while I have properly installed the reflux modification offered for sale on this site, I am currently having some problems with it that we are attempting to work out resolutions to. Until these issues have been resolved, I will cautiously recommend against purchasing this modification from Brewhaus, but I will address your questions as if we were talking about any 'valved reflux' still.
1, Not exactly. Given ideal conditions, you should be able to extract spirit of a similar quality from the Essential Extractor II Pro unit. Unfortunately, these ideal conditions are a bit more difficult to obtain and maintain with the stock setup, because, like I mentioned earlier, it is based purely on water flow and temperature. To be sure, you can be extremely inefficient with a valved reflux still if you don't know what you're doing, so, while the modification will not make a more pure product in GENERAL, it should make a purer spirit EASIER to obtain. The difference may only amount to 5% or so, but this can mean worlds in terms of flavor and odor profile. Once again, I have no empirical data on this PARTICULAR unit as it does not work for me at this time, but this applies to valved reflux stills in general.
2, Cooling lines are still used with this modification, but only for the condenser. In theory, the inverted condenser causes all of the liquid to be returned to the column the way they came in, creating the reflux that was originally caused by the primary cooling lines. At the current time, I am experiencing choking issues in the condenser that necessitate cooling with the primary cooling lines, but hopefully this is an atypical scenario.
3, You DEFINITELY still wish to maintain a constant temperature. This is the most important aspect towards creating a purer distillate. The temperature is maintained by the laws of physics. So long as you are extracting a relatively pure single substance, the temperature at the top of the column will stay at the boiling temperature of that substance. By drawing off the distillate at the proper rate, you disturb the equilibrium as little as possible, thus keeping the vapors from growing turbulent and mucking up the purity.
4,6, This refers to the 'proper' rate, I mentioned above. Generally, a 10:1 reflux ratio is considered ideal. By this I mean that, for every 10 units of vapor condensed, you draw off one unit, with the rest returned to the column. In order to determine the amount of vapor your boiler can produce, there are some simple calculations to perform involving the heat source you're using. 'Making Gin and Vodka' by John Stone details this pretty well, but also says that you should be prety much all right with 4ml/minute.
5, The general consensus is to operate the still on full reflux for about an hour. Granted, the brewhaus still is fairly tall and should, in theory, be at equilibrium by the time the vapors rise to the top of the column, but it's always best to wait a while and let things even out anyway.
7, It's 1/4 OD, I think, and it's about an inch and a half to 2 inches long.
8, Filtering is a pain in the ass, because you have to dilute down to 40% and then you have to sit there and pour it through the charcoal again and again, and you have to wash the charcoal or else you get dust, which negates the filtering and blah blah blah. Filtering is fine and dandy if you screw up, or if your still doesn't quite hit maximum purity, but why bother with it if you don't have to? Plus, I like having an ultra-pure distillate for maceration because it's a much more effective solvent at higher concentrations. Also, certain liquers are made from a more concentrated base.
9, The jury's still out on this one, Scott. If we can resolve these choking issues I'm having, hell yes. It's a great way to convert an already solidly-built stainless reflux still into a full-on valved reflux still with little compromise in the way of structure or craftsmanship.
If, on the other hand, these issues can NOT be resolved, there is no way I would buy it again. It permanently alters the still by cutting the tube leading to the condenser, and if it is ineffective, then it is an $85 exercise in futility.
A lot of ifs here, and a lot of information left to be discovered. We'll see what happens. At this time, again, I cautiously recommend against it.