Hi there,
I read on the Wiki that there was something called a clustering penalty applied to Sentinal frigates and Electric bombers, but I can't actually find any documentation on what it is or what, exactly, it does. There's absolutely no in-game mention of any clustering penalties that I can find (though I may not be looking in the right places), and there's no definition on the wiki, either. I'm assuming it does something bad if you have too many ships of the same type on a planet, but that's just a educated guess on my part.
Is there some documentation that I could read on this subject?