So since I already got ahead of my self and started building the box with my original port height of 4.5 inches, the question is, do I need to slide some MDF in the port to bring it down to only 3.75 inches? Of course, that will change my box volume slightly as well which will change the port length etc. At 4.5 inches tall, I'm looking at a first port resonance of 164Hz. Is that too low? When I thought my box volume was 14 cubic feet, it was 189Hz which is what I wanted.
All these issues will be corrected on the second box. I haven't started assembling the port on that one yet.