You're quite welcome.
Okay, here's what I suggest: Inner dimensions, 27" tall by 17.25" wide by 13" deep. You can adjust these dimensions as you see fit, keeping the internal volume within 5% of 3.5 cubic feet.
Woofers in a vertical stack on the front of the box, window-pane style horizontal brace in between the two woofers, to stiffen the box.
Install four 3" diameter ports, made from PVC pipe, each 6.0" long. They go on the rear of the enclosure, with at least one lower than the magnet of the bottom woofer, and at least one higher than the magnet of the top woofer. This will allow some "chimney effect" cooling as hot air exits the top port(s), drawing cool air in through the bottom port(s).
Cover roughly 50% of the inside surfaces with 1" thick open-cell foam, I use WalMart mattress topper foam. It's gotta be open-cell foam - if in doubt, try blowing through it. I use spray-on glue but use whatever you want to hold it in place.
When you buy the PVC pipe for the ports, get four 3" diameter expandable plumber's test plugs, and make sure they actually fit your 3" diameter pipe (sometimes the inside diameter is less than 3"). These are your secret weapon. With all four ports open, your box is tuned to 48 Hz. With two ports plugged (ideally leaving one high and one low still open), the tuning frequency drops to 35 Hz, tightening up the bottom end. Plug all four ports and, you guessed it, sealed box. Three different low-end voicings. Actually more than that - you can also try one port plugged, or three ports plugged.
I like to glue some 1x2 white pine edgewise between port cut-outs to strenghten that area, as otherwise it's inherently weak.
My guess is that two ports plugged will be a good starting point. I would expect all ports open to be too boomy, but I may be wrong, as I'm just making assumptions about your woofers.
One more thing - let's trick out those ports a bit. Chuffing sets in when the airflow goes turbulent, and that will happen at the inside opening first, because the flush baffle around the outside opening helps to funnel the airflow into it a bit (think of the air as behaving like water flowing through a pipe). To reduce turbulence at that inner opening, we need to make the opening larger. So cut that inner opening on a 45 degree angle, and now you have a large oval opening of greater cross-sectional area than if you'd cut straight across the end of the tube. You want the measurement down the centerline to be 6 inches. This will help delay the onset of chuffing a little bit if you really push the cab hard. If you decide to do this, make sure you allow adequate clearance for the woofer magnet, as the long side of the port will now be a little over 7.5 inches deep.
Okay all this port area, plus the angle-cut ports, is probably way overkill for these older woofers. That's okay, this stuff won't be overkill for your next generation of 12" woofers. This box will work with any Eminence 12" woofer suitable for bass guitar, so when you're ready for a bit more punch, you'll already have the box made. You could even drop in a pair of the mighty Kappalite 3012LFs and have an honest 900-watt capable tweeterless bass cab.
Feel free to do whatever you want of course, these are just suggestions.
