"There is a optimal ratio for slot port width to height of 4/1 for a reason. Do you think a 1/4" high x 28" wide slot port, with a cross area of 45 cm2, will work the same as a 3" round port (45 cm2)?"
i researched around a while back on this topic and could not find any consistent information. many surprisingly narrow ports are found in good performing speakers and subs.
take for example how genelec ports its top of the line $36,000 studio monitors:
those are 18" woofers run full range.