Modders,
I've noticed folks going overboard on their bounds polygons. What I mean by this is: "using more coordinates than absolutely necessary to evoke a convincing level of hit-detection in-game."
The question you should now be asking is: "gee Trylobot, if you're so smart, what the heck should I be doing instead? I haven't noticed any problems."
Good question modders, I'm glad you asked. The problems you haven't noticed are insidious. They don't really affect anything at small scales. But when your ships are used en-masse, say in a mod compilation like U.'s Corvus or similar, these super-complex bounds polygons will slow down the computers belonging to the "economy / mid-range" level. In other words, not hardcore gaming machines like you and I are so fond of. And you should be worried about this, because these folks are technically your audience. You're going to all this work, authoring this mod, ostensibly so that as many people as possible can play it. So you want to Optimize.
Best optimization: consider removing literally every bounds coordinate you currently have and making a new one from scratch. If you want to look at perfection, load up some of the vanilla ships and look at their level of detail. Then think to yourself, "self, if the bounds polygon looks like this, and in-game I didn't notice anything funny, then isn't this enough?" The answer is yes. Yes it is. Use as few bounds coordinates as possible to look right, and not a single one more. It's better for the game, better for performance, and better for the perceived quality of your mod.
EDIT: Here's an example from Ghoti:
Spoiler
(http://i.imgur.com/2hvPiFZ.png)
This concludes a Public Service Announcement.
Update: April 19, 2013 - PRO TIP from Vinya
Use your image editor's "Pixelate" effect, and give a size of 5 (or higher). When setting up your ship's bounds, use this pixelated version of your ship. That way you won't be as inclined to include unnecessary details in the polygon.
Update: Addendum from Astro with illustrations (http://fractalsoftworks.com/forum/index.php?topic=4270.msg66788#msg66788)
(https://dl.dropbox.com/u/66536185/clam_bounds.png)
I thought this was a joke
Spoiler
(http://dl.dropbox.com/u/6581181/notajoke.jpg)
THIS WAS NOT A JOKE.
Spoiler
(http://dl.dropbox.com/u/6581181/screamer/1gentlemen.jpg)
(http://dl.dropbox.com/u/6581181/screamer/2lets.jpg)
(http://dl.dropbox.com/u/6581181/screamer/3rock.jpg)
and yes
Spoiler
(http://dl.dropbox.com/u/6581181/screamer/4andyes.jpg)
This isn't nearly as funny as nyan cat though >:(
Addendum to the Public Service Announcement:
There's been some worry here about the desire to have hard guidelines about how many boundary-box vertices are enough vs. too much. To echo Trylobot's advice, there can be no absolute limits here because the solution is not a single number value; it's a relative range of effect, dependent upon the complexity of the sprite in question. But total surrender to the over-intricate aesthetics of any given modded-made sprite is definitely not in anyone's best interests.
At this point in the discussion, I thought it would be helpful to provide some concrete examples of what to aim for. Here are some examples of the bounds polygons for official Starfarer units. These guides should help greatly -- please compare them to your own modder-made creations, and you'll quickly get a better feel for "how many is too many". Official ships often have quite a lot fewer bounds points than you might assume they do.....
Spoiler
(http://i1098.photobucket.com/albums/g372/mentor_of_arisia/starfarer/official%20bounds%20polygons/Apogeebounds.jpg)
Spoiler
(http://i1098.photobucket.com/albums/g372/mentor_of_arisia/starfarer/official%20bounds%20polygons/Aurorabounds.jpg)
Spoiler
(http://i1098.photobucket.com/albums/g372/mentor_of_arisia/starfarer/official%20bounds%20polygons/Conquestbounds.jpg)
Spoiler
(http://i1098.photobucket.com/albums/g372/mentor_of_arisia/starfarer/official%20bounds%20polygons/Sunderbounds.jpg)
Spoiler
(http://i1098.photobucket.com/albums/g372/mentor_of_arisia/starfarer/official%20bounds%20polygons/Tempestbounds.jpg)
Everyone can now see how when it comes to bounds, additional data does not necessarily equal additional useful information. Ships can and do get by just fine on surprisingly few boundary points. Coverage of engine exhausts does not need to be encyclopedic in its scope; that's often the first place one can delete several vertices from modder-made ships.
And even some official ships can afford to lose a few bounds, as we saw with the Conquest. The Astral is difficult to meaningfully slim down its vertex count further, while the Paragon can definitely afford to give up as many as 8 of them.
There are many customers of Fractal Softworks who do not fit the assumed profile of "serious gamer" from a hardware standpoint. It is very important to remember that. Even if someone does have a moderate-performance box -- instead of a 10-year-old computer stuck with WinXP SP1 and only 1024MB RAM (how soon we forget) -- their graphics card may still be well behind the curve by a rather wide margin. For reasons of technical know-how as well as basic finance, many of these acceptable but unspectacular machines are unlikely to improve. It is not reasonable to cut these folks out of your audience when you spec out mods which include ships of fiendishly-clever but also unnecessary complexity.
The RAM, CPU and video card of many older computers thank you for your friendly restraint. ;D