As much as I think it to be a time consuming issue, I just think if you're using range rulers that much in placement, you have too strict a guide for this game.. eyeball it, just to ease the placement of the thing. And then make sure you set your ships where its more advantageous for you..
I think using 2 range sticks to place an asteroid is just something that my opponent will hear a big sigh of impatience from me.. and then I'm going to reconsider my starting placement to make sure I screw up his perfectly planned out first move... I may even come across the top of that asteroid just to piss him off