I don't think there's any point to barrel rolling that much.
vohl sq is a fast track anyway, barrel rolls only really seem to be of use if you'd have been slow in that area to begin with.
as lunar stated it's possible to stick remarkably close without doing ANY rolls.
in race mode I would probably only do 3 a lap on vohl sq, trying for more is simply inviting disaster because all that time spent wobblig the controls is time not spent keeping the ship on a fast line