It's debatable what Vegetto meant by "force me to show my full power", which could indicate higher forms like SSJ2. But he not showing his full power as a SSJ and easily dominating Boohan could easily work with a 2x gap, as #17 also one-shotted Piccolo when not even using his full power with a gap similar to that.
Vegito has a different purpose than #17. He wants Boo to absorb him therefore he needs to make Boo desperate enough to do it. It doesn't matter what kind of gap that was.
He was still holding back, but yeah, you are right that Vegetto never attempted to oneshot Boo. But all I'm saying is that Vegetto's feats against Boo are tangible with a 2x gap, which is bigger than the gap Goku had on the Ginyus in their fight. I don't see a need to go with more than that unless I wished to keep base Vegetto up there, which isn't really needed manga-wise.
I've always put Base Vegetto on par with Gotenks Buu (Worst case scenario for me), although I'm not opposed to Base Vegetto = Gohan Buu (Although since the anime is all we have, I go with the former with Buu mentioning him holding back against Base Vegetto).