Just as a quick note: Every time you "double the size" (make it twice as long, tall, and thick), you actually octuple (by eight) your mass, not by three/tripling.
That's because you are "doubling" the ship in each direction (all three of them), and each time it doubles the mass of the ship. So three doubling-s equals an octupling.
And just to be sure that Avorion followed the proper laws of physics, I popped in and made sure that doubling a ship (in this case a simple starting block) would octuple, and it does (see below for my notes):
Size
Mass
Delta
2³
0.41
N/a
4³
3.26
7.95121_
8³
26.11
8.00920...
Both delta values (mass divided by previous mass) are within the assumed rounding-error range of eight that I'd say it is safe to safe Avorion follows the square-cube law.
What?
When you have a cube and want to bobble it size you simply remove it's armour on 3 of it's 6 sides, copy the existing cube and paste it in 7 times to form a new cube. To exactly calculate the loss of mass due to removal of armour is impossible but you still have to do it to be accurate because it's a lot. Secondly it's an simple 700% increase of volume, with some of it's mass still intact. But removing those 3 sides of armour before copy and pasting it in to a new cube removes a huge amount of armour you don't need in the middle of a cube.
Also worth noticing that overtime you double your mass you need to more then double your thrust to get the same result, in real lift that is. So if the game where to use more realistic approach here this huge cubes would not be a rpoblem in the first place.