The 338 Edge is in fact simply a 300 Ultra necked up to .338. I run the 300 gr. SMK out of a 30" tube between 2850-2950 depending on load gun etc. Under the equipment section there is an extensive thread on the EDGE, with lots of info from myself and many others that have them or have built them.
With a 26" barrel and lighter bullets like the 225 it was hardly worth the additional work for the little velocity. If you are going heavier say the 300's it is worth it at any barrel length or if you are using a 30" or longer tube it is worth it with any bullet weight. I would expect the 27" tube to get around 3200 fps.