According to the brochure specs, the chaffer length and witdth is the same on both the 9400 and 9600:
Length is 32.7 and width is 50.6 inches. machines are same except for walker length, and engines.
Unless you are cutting light yielding grain, not more than 40-50 bpa, I would not advise a 30 foot header. An L gleaner would not handle it either, probably less capable than a 9400.