In general terms it's the Heads you want to avoid because that's where the majority of the gut-wrenching, head-wrecking components are to be found.
The Tails, for the most part, smell feckin' awful and taste even worse.
If you start off separating an amount of distillate, at each end of each spirit run, that will isolate the Heads and Tails completely, you will be able to recognise the smell and taste of these fractions. You will then be able to learn how to adjust the amount of each fraction to be recycled and how much of the late Heads and/or early Tails you want to include in your spirit to achieve the result you want in your glass.
On the other hand if you start off adding lots of Heads or Tails or both into your spirit your palate will get used to the taste and you will be unable to tell the difference by taste or smell.
50ml I recommend to cover Foreshots is way overkill. Normally, from a 4lt batch of low wines, 20ml is considered by many to be enough so in making recommendations to others I decided to be absolutely, totally and undeniably certain and recommend 50ml.
One thing to remember is that while Foreshots can only be ever used as a cleaning agent the Heads you collect will be recycled and yield drinkable alcohol at a later stage.
Heads are usually around 70-75%ABV and this means you only need 1.5lt to do a Heads run. (1.5lt @ 75% will make up a 4lt fill for your Airstill when diluted to 30%.)
At the end of the day, it's your still and if you're getting what you want from it that's all that matters. Some distillers strive for perfection, some want to make all sorts and fill their drinks cabinet, others, like me, are content just making what me and my other half drink.
AM
