The cut off at 20% is a little subjective, as is the 1.35lt figure. In reality you can go for either but probably not both to an exact degree. If you have a 17% wash you will probably hit both targets. If you're wash finished at 14-15% maybe not!
Either way the Guide to Running an Airstill is just that - a Guide. Use it to point the general direction, in terms of how you process a wash through an Airstill, stage by stage, rather than as an exact dictat to be followed to the letter.
As a suggestion, if you are cutting off at 1.1lt at 20% you could process that on to a spirit run and end up with a little less finished spirit - very little difference overall. 
Alternatively, you could let it run on to collect 1.35lt regardless of ABV at the end. Either will result in Low Wines that have been stripped of the very worst elements of the wash and, after all, the actual purpose of the Stripping Run is to extract clean Low Wines, containing mostly ethanol and water, from, relatively, dirty wash containing all sorts of dead yeast cells, spent nutrients, minerals, unfermented sugars, etc., etc.
In the end the difference in final spirit yield will be quite small and squeezing every last possible drop from a wash is not supposed to be the objective.
Please, also bear in mind that, as said earlier, the Guide to Running an Airstill is just that and should be read with in conjunction with my guide to spirit cuts Spirit Cuts for Beginners.pdf and any other info you can find on the same subject because, at the end of the day, Spirit Cuts need to be done by taste and smell rather than by physical measure.
The Airstill guide gives amounts to collect at each stage and this will get you part of the way and help a user to produce a drinkable spirit, albeit with some impurities that they may prefer not to have.
The Guide to Spirit Cuts will, hopefully, improve the beginner's knowledge and help them to learn by doing. That's the theory, anyway.
AM 
Statistics: Posted by Almanac — Thu Nov 15, 2012 9:55 am
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