currently that's what i do - multiply. but it's a pain in the butt when one wants to try out a variety of line spacings quickly to see what will fit best. if i just have a parameter in an object that will space out the lines until they're out of room within the bounds of the object, then it would save a tonne of time!
to be clearer about it, when i say a paramter i just mean a box in the object settings that says "lot width" or something - so that i can change it from 6000 to 6200 and see the effects immediately. our office does a lot of condos too, and it would be handy for quickly laying out grid lines!!