Hedlund BLH questions


I am interested to build the Hedlund horn, but before I would like to make some simulations to "see" how would operate the horn with different drivers.

So, my questions:
-what is the correct St (3x23cm?)
-what is the correct Sm (65x23cm?)
-what is the correct line lenght?
-what is the horn contour? exponential?

Is there anybody who built this horn and has some experiences?