I also have Future Trunks SSJ being 2x Frieza (100%). Completely ignoring the scouter numbers.
I like the formula that believes that when it's a fight of many characters against a stronger character, the formula would be this X1^2 + X2^2 + ... vs Y^2.
For example:
Frieza (Namek) = 100
Future Trunks SSJ = 200
It would be equivalent to:
10,000 + 10,000 + 10,000 + 10,000 vs 40,000
This is all because Future Trunks would not be receiving the attacks of the 4 Frieza at the same time.