OK, I'm posting what I have so far, and to ask for more data. I really need more examples to work with.
I've refined the formula to this:
k + (k * m[SIZE=1]0.2[/SIZE] * q)
q is a constant in the ballpark of 0.565917 - but I'm still refining (it's probably no more than +/- 0.00001). I'm sure this number has a significance I'm missing, otherwise it's a very odd figure.
For just the FFSS, k is about:
HMC 9654
WW 64831
AW 96931
IW/RW/Garbage 300
First discoverer is a 2.6 multiplier.
Still working on terraformability, but for HMCs it's about 100677. Terraformability is still a range.
This formula also works for old scans and payouts if you multiply up by 2.4 - which correlates nicely to the +100% and +20% bonuses bodies have received since the early days.
DSS is... trickier. There are individual multipliers for different parts when using DSS - but at the moment I'm not sure they're straight multiplied up. I'm close, but between not having enough data, random bugs, and terraformability not always being 100%, it's quite the headache. More data required.
Data needed:
Body type, body mass, terraformable? First Discoverer? DSS'd? If so, First Mapped? Efficiency bonus?
Also need data on stars/neutrons/black holes:
Body type, body mass, First Discoverer ?