Here is a weight and Balance calculator kindly submitted by Andy Hollitt
Checking the CofG position involves a fairly simple formula and if you don't like maths, go to the Australian Jabiru website where there's a calculator to do the work.
But what would happen to the CofG if you put a 3Kg tent right at the back of the tailcone? What about a full 20 Litre plastic jerry can behind the main tank? Just how much lead is required in the ventral fin to balance at the forward CofG?
To answer these questions you need to get in to moment arms, which seemed a bit complex to me. So I wrote an Excel spreadsheet to do the calculations, at the click of a mouse! Note that it only applies to the SK model as it stands (arms will be different for other models), although it's simple to modify the spreadsheet formulas. I'm interested in feedback, and can modify the spreadsheet for other models if emailed a proper W&B sheet.
SK Weight and Balance calculator