A few questions - reflux still

[ebswift]

As a background I've got a boka slant plate 2 1/2" stainless still with a fairly tall column with a lot of copper packing and a condenser that works well enough to not let any vapour out. For all intents and purposes it appears to work very efficiently. I use gas and it has a fast start-up and no problems maintaining heat. The boiler is an old autoclave which I think was about 40 litres. I've been making 25 litre washes so it has a lot of breathing space. Product I am looking for is high purity neutral. So that's the background, now I have a couple of questions about operation which I can't find any concrete information on.

Firstly, how does one determine the optimum take-off rate? While there are probably equations that would answer this, I reckon calculating this would be very difficult outside of controlled environmental conditions (like a lab). I have done enough research to know that the 'rule of thumb' is to run the take-off of the hearts at a thin, barely broken stream. I also know that there is much talk about larger diameter columns being capable of producing product more efficiently and faster. The 2 1/2 inch column is likely moving into this category (of being able to shorten run times), so how do I work out the optimum? Do I run it very slow and work out the maximum purity (currently at about 93% when run at a dribble), then run it faster until the purity declines and wind it back? Or can it be wound up until the temperature rises, then wound back? Basically I don't want to be sitting there for hours with a dribble of a take-off if it is capable of running twice as efficiently as I'm operating it. I am aware that with smaller columns and/or less packing, you have to keep it slow to get higher purity neutral. If the dribble is the optimum I'm of course happy to stick with that.

Secondly, the time to get to equilibrium in the column. The Compleat Distiller suggests 2 hours to let the column equilibrate. I see people in the forum mentioning such things as 'at least one hour to an hour and a half'. How does column size and packing height measure into this? Are there longer or shorter times for larger or smaller columns/packing heights? Is there some measurement that helps to determine equilibrium?

Thirdly, going from foreshots to heads I'm not seeing any temperature differential and the smell is a little hard to differentiate. I'm taking maybe 50ml of foreshots, then once again as per The Compleat Distiller, taking 1cup of heads (because once again there isn't really any telltale with separating them). Trying that today, the first take of hearts seems pretty good - I don't detect anything untoward in the mix. I'm not trying to squeeze less than 1cup of heads out of the equation - quite the opposite, I'll take more if there is a better way to differentiate. In contrast, with this still design, tails have all kinds of telltale signs - the ethanol purity drops, the smell comes into effect, and the temperature begins to rise - temperature is the last thing to change at the tails in my rig.

Whilst I can probably do comparitive tests to work some of this stuff out, I know that much of that has already been nutted out (as have the still designs). I do like to work things out for myself with the help of some research, but on these topics I'm not getting definitive results from searching. I also severely lack time so I can't be tinkering with too many tests for the sake of reinventing the wheel. Even given the answers, there's still a hell of a lot that is going to simply come down to experience, really taking notice of what's happening, and most of all recognising subtleties that are going to affect the brew for good or for bad (and in the process, developing the taste and smell for it). So I would really appreciate any experience on these questions. Thanks in advance.