For the purposes of this analysis, you can assume that they're
off-the-shelf drives, just larger ones than are normally "rated" for
the hull (that is, a drive several sizes smaller will get the max 6Gs
when this ship is "unladen" - however, a 400-ton ship will be able to
tow a 3600-ton hull at 1G). That's one of the reasons that the hull is
a custom hull.