Couldnt get any linking data today but:
20Con+21Arc Duo, no aspect, numbers for the 20Con.
Dodo 3 Star: 139
Dodo 2 Star: 116
Dodo 1 Star: 93
Footpad 3 Star: 129
Footpad 2 Star: 111
The Dodo numbers drop -23SP with every star. If you work downwards from 3(or 5 if the data went that high) this will result in varying percentage drops(16.x%->19.x% difference from 3->2 then 2->1), which wouldnt make sense. So more than likely, it increases by a set percentage from the 1 star numbers.
23/93-> 24.73% increase for every star on the Dodos.
111-18 (estimate 1 star footpad if the decrease were the same like dodos) = 93 again, coincidence? 18/93 = 19.35% increase for every star on Footpads
Small sampleset doesn't seem to show a definitive pattern, except for the starting point of 93SP for 1 Star. Solo numbers would be better than duo as it could be the party aspect causing non-consistent increases, I'll try that tomorrow. If someone wants to beat me to the punch its pretty easy to get the numbers... just start a leve, kill something, lower stars then kill another.