Measuring Enclosure Size

When building custom fiberglass sub enclosures (something like a stealthbox), how do you measure the interior volume? 

Specifically, if I want to build a sealed box with 1.6 cu ft (for instance), how do I plan out the size of the fiberglass base, the spacing F to R, bracing, all that good stuff to come out with the right size?  Should I just overbuild it and stuff it with batting? 

Are there any tricks to compensate for an over/undersized box once done? 

Also, what's the best way to attach the box to the vehicle once done?  I'm thinking T-nut in the FG, but would that overstress the point it's inserted into?

Thanks!

Oh, OK - now I see the Sticky on foam peanuts & measuring volumes.  Sounds like I guess (big) based on rough measurements, build the base & fill with foam/water/sand - maybe all three for the hell of it.  If it's too big or small, any easy fixes other than re-sizing?  Maybe fill with some peanuts?  I guess I could just leave some water in there.  In a bag.  It probably won't leak...

And someone said Caps=Evil.  What's that about?

Jeff

Where can you find Dacron filler?  Also where can I find printable copies of the articles done on your work?

Jeff, I heard that before, but I don't follow how it could work.  Seems like if I stuff it like that the sub would see more air resistance (meaning less air volume).  Have you tried this - does it really work?

Also - any thoughts on how to attach the sub box to the vehicle?

oonikfraley00: so could purposely make an enclosure smaller and use that stuff to make up the difference? would it sound the same as an enclosure that had the correct airspace without the dacron filler? thanks

-ryan