Yes, I think 3x4 or 4x4 would be more appropriate.
I have over 170 plots free so it shouldnt be a problem to build high enough. And I will get more (lvl 39 atm).
I thought you wanted us to plot out in the road as well, so that would allow some stuff to stick out.
But maybe you want the airspace above the road totally free anyway (exept the bridge). That is perfectly ok and I will keep it within the borders. No problem.
Yeah, I just wanted to show you something. There will be roofs, I promise.