Seems like everyone is going to have to make some type of modification to the KAB 4 or 6.
Some it will be the height of the burner (4.25"). Some it will be the size of the cooking surface. Yet others will have both problems. So im going to try and fix what I can and shed some light for anyone who wants it
I have a banjo burner from NB that is being used in another system
This burner worked great at 4" from the burner with a flat bottom pot. The brackets are to make the cook surface bigger. Once we switched over to the keggle the flame was not as effective. Since the keggle has a domed bottom there was too much heat loss. (I hear others have a height problem too!) Our solution was to turn one of the brackets around to allow the lip of the keggle to sit into the void. Now the bottom the the keggle is about 2" from the burner. Heat then runs up the rounded bottom and raises temp. much faster. Ive never timed it but we have never had to wait on boiling water.
First Mod: Raise the burner. The Four legs are 1/2" round stock bent in a rectangle, welded to the thick wind screen in three places, The top and bottom are on one side, the middle is on the other. I used a dremel with a flexible handle attachment. (used two big metal cutting blades to cut four legs) An angle grinder should work too.
Using u-bolts and a few drilled holes I re-attached the legs to the wind screen.
A Few things I noticed: There are nubs on the burner that could get in the way of the u bolt. I got lucky and was able to squeeze mine in.
Also remember the bottom of the keg is not always going to be level, or your base, so you may have to play with your leg heights if ya got a wobble.
According to bayou classic: The re-engineering of this burner was to optimize the burner with a flat bottom pot. The rounded bottom of a keg is not optimal.