SG and fuel distribution
Your flight plan is based on a fuel burn in kilos/hr I assume. It doen't matter what the SG of the fuel is, you just want a certain fuel load weight and so the distribution will be unaffected. Your fuel load is displayed in Kgs, your burn rate is measured in Kgs and your fuel burnt is shown in Kgs. You plan to arrive at destination with a certain weight of fuel remaining. Don't see where there should be any problem with the fuel being of a SG higher than .785 Kgs/litre, just means the volume required for a given weight will be less.