Very happy to hear that you have been enjoying the Sierra-2!!!
I actually built some front slot port sample cabinets a while back -- even posted some pictures of them. After thorough evaluation, bass performance was compromised by this design. There was just no way to make the slot port with enough area with the tuning required that would allow for uninhibited air-flow of the rather exceptional movement the S2 woofer is capable of. The cabinet would have to be quite a bit larger, thus changing the overall design and adding additional expense
See here:
http://forum.ascendacoustics.com/sho...4382#post44382
Sorry