A very helpful warning, in that case I will try to stay away from round shapes and just resize the grid and snap values if I wish to build a big ship so that I can use large blocks instead of many tiny ones.
However, I feel that this is an issue that need to be fixed. If it's a hardware limitation, having the game detect these bugs and warn you to stop building so much would be nice, and if it's not then it really should be taken care of - nothing is going to stop people from building bigger and more complex! I suggest that you report the bug, using the logs and such if you still have them, since it might not happen for others? (I wouldn't know, I've never bulit something that large in terms of block amounts)
Oh and also, having rounded shapes actually programmed into the game would be nice. 1/4 circle (◕?) 'edge' blocks, corners; in short blocks like the currently avaiable ones, but for round shapes. I have no idea how the game does its magic internally (And I don't want to, my poor head might implode) but it doesn't seem that difficult and I'm sure it would be a loved addition by all the builder type of players. I've thought on many other things this game could use (although it's amazing already) but admittedly I've refrained from making suggestions because the game is still being developed actively and going through the forums the dev seems to have acknowledged. Chances are this is one of these things (let's face it, ''round blocks'' are not exactly a novel idea) that are waiting on the pile of 'things to include in the game' until the dev can implement them.