Here is my (almost)finished Stage 4Pi(missing the grill). It sounds GREAT! It has more authority, deeper bass, and fuller sound than the well regarded 2Pi Tower.
I decided to mount the horn outside the box and the vent to the back baffle. This gave me more height without changing speaker box demension.
I also used 10uF and 8uF motor run caps in place of polyprop ones. I tried both caps and found motor run caps provided "slightly" fuller sound.
I would like to thank both Wayne for providing the speaker plans and GarMan for his many helpful emails.
Cheers.
Norbert
http://home.cogeco.ca/~nlee137/speakers/4Pi-stage-mod.JPG
http://home.cogeco.ca/~nlee137/speakers/4pi-Xover.JPG