Altec 421-8H Series II Box Size??? Any Ideas Where To Start?

[hemicuda]

Howdy, just got a couple of Altec 421-8H Series II speakers I wanted to put in use. I was wondering what the best size box is to put them in? I would like them to be able to play to down as far as possible and flat as possible also. I know I'm not going to get any "real" deep bass but I want to get as much as possible with good power handling. I will be bi-amping these using a couple of 811b horns that have 808A drivers (with alum. dia.) and using a Samson 2 way electronic crossover that has CD horn compensation, low frequency delay and limiter. I'll drive the woofers with an Altec 9444a/sa amp and the tweeters with another Altec 9444a/sa. They are rated at 200 watts per channel @ 8 ohms. I've found the theile-small paramaters and have fooled with them in Bassbox pro software. They just don't look too good no matter what I do with them. I can get the -3dB down to around 55 or 60 hz with good power handling and flat response using between 3.5 - 6 cubic feet with the port tuned to 60hz. I do have some old 1202B cabinets I can put them in but they have a big square port. Not sure where those are tuned to. Anyways, I'd appreciate any help on these. I'll be using the speakers for "hi-fi" setup only. Thanks!