Thanks for the info, Giskard. I was hesitant to use triangular ports, but it was the only way I could squeeze them onto the front baffle. In retrospect, I should have just used round ports on the rear (with the appropriate elbow bend).
The 2 cu. ft. stock volumes of the S9500 seem small. I used an Eminence design program (I think it's a re-badged Bass Box program) to come up with the volume I have. Anyway, I'll probably just build new boxes (I own the table saw and MDF is cheap!). Now all I’ve got to do is find some more time.