@GWG
More I was commenting on the fact the OOC thread has comments on stuff from all the other threads, so it's harder to keep things straight in my mind. I didn't really mind reading through lots of OOC anyways, so it's a downgrade for me. I understand that lots of other people prefer it though.
As far as the profile, if you have weapons with drop, a flat but short target is harder to hit than a tall but thin target. You wouldn't have to have it fly above it's target, and even if you did, a large percentage of it's area is visible sky from below. It's really hard to shoot the rotors themselves without a continuous laser, so you'd have to target the central box, which is a far smaller target.
As far as erratic flight patterns, one advantage of the four blades is that the quadcopter has complete control over it's movements. Assuming you have a good targeting CPU, it can completely predict what movements it'll make and compensate. But even an animal with a fairly regular gait like a horse can't predict it's own movements so well because the ground varies. It's not a big problem if you're running in a steel corridor where the floor is regular, but it's a big problem in uneven terrain.
@Sean
Yeah, they're vulnerable to losing a limb. But it's nearly impossible to hit one of the limbs without a continuous beam weapon, which are fairly easy to armor against. Anti-ballistic armor would only be needed for the center, and depending on how it's used you would only need to armor the bottom or sides.
As far as losing a limb, I'm told a quadcopter is vulnerable to it, but that it would mostly lose lifting power and manueverability. Apparently, you can take two opposite limbs out and it can still "fly", by spinning. You would have to further limit the weight, but it would be able to retreat even if it sustained major damage.
If you're really worried, you can make it an octocopter, which is able to lose half of it's limbs and still fly with nearly peal manueverability. It'll lose half of it's lift, but it won't be crippled.
Compare to an RT, which is a horse. I hope you realize what they do to horses that break a leg.
Also, the hobbyist that has been arguing through me told me to post this link:
http://m.youtube.com/watch?v=w2itwFJCgFQ#@Radio Controlled
Thanks for the special mention, although NAV and SS did waaay more than me. I'll try to put more work in in the future.