The only change to the port is to shorten it to two inches long, The Lowther has a higher fs then the Fostex so the enclosure needs to be tuned higher.

If you are using a correction circuit you may also need to reduce the parallel resistor a few ohms. Take a look at my updated correction circuit values in Project 5 and select a smaller resistor then you are using and the corresponding inductor. I also found that adding a small cap in parallel helped bring up the high end a little, this cap and its value is shown in my Project 4 final circuit.

Hope that helps,

Martin