I usually have Zarbon at 88% of Vegeta, so Goku being 90% of Cell seems to fit there well. But, I know you have Zarbon at an even lower percentage don't you? Vic always like to bring up that KKx2 Goku quits against 18,000 Vegeta which would be around 88%. I can go either way personally.
90% seems like a good range where Goku is still a rival more or less, but outclassed.
What do we do about Gohan and Cell's higher powers? I think this model is perfect for everyone to work with.
Gohan 120
Cell 120
Cell 100
Goku 90
Vegeta 60
That's a damn good model for anyone. Let's try SSJ2 Gohan, PC, Buff PC and SPC added to it.