My Robin has a main fuel tank holding 110 litres and an auxiliary tank holding 50 litres. In the Weight & Balance section of SkyDemon I seem to have to set the main tank fuel quantity in litres and the auxiliary in kilograms. I’d prefer to enter both in litres. More significantly, in the Flight Details section, the Fuel slider will only go up to “110 ltr” even though I show the auxiliary tank as carrying 36 kg (ie 50 litres) ie full fuel. How do I get the slider to go up to 160 litres?

You cannot have different units for different fuel tanks.

If you have specified different fuel tanks you need to set their contents separately. Since they'll have different CoG values it's not possible to simply set the total amount of fuel, as SkyDemon won't know how it's distributed between tanks and therefore won't be able to do a weight and balance calculation.

Could I suggest giving our support a quick call? They'll be able to talk you through what might be wrong with your fuel tank setup much more efficiently than going back and forth on a forum. I'm sure it'll be straightforward to sort out.‌ ‌‌

Thank you for posting a follow-up which could help any other people running into the same problem. Glad it's sorted.