Nice looking BR-6, Hans.
The gauge of string is dependent on the tuning(s) you want to play.
Most of the time, I play C6 tuning. After some experimentation, here are the gauges I have come to prefer on my Gibson lap steels, which are all approximately 22-1/2" scale:
E .017
C .020
A .024p
G .026w
E .032
C .038
The above gauges work fine for A6 and B11 as well.
Although some may be appropriate for low-bass G, A, D, or E tunings, as a rule, standard guitar sets are usually not the best for lap steel. It's better to purchase strings by the gauge, not the set.
Here is a link to a chart courtesy of John Ely that will get you started:
http://www.hawaiiansteel.com/graphics/p ... _chart.pdf
A degree of experimentation will probably be needed before you find out what works best for you on any particular instrument.
