I would disagree with the higher number gauge wire for a barrel piano.
I have restored several of these and I always use the original size
wire sizes.  I had this problem demonstrated dramatically when I got
one big hulking Hupfeld barrel piano with the treble strings all
replaced with a larger size.  They had tried to put larger wire on,
to make it louder, I guess, but it just broke the cast iron plate.

If you want to go fully historic on these use pulled iron wire as used
in historic fortepiano restorations.

Putting a larger wire in the treble causes _much_ more tension to be
necessary to get the right pitch.  These units are often without cast
iron and you should never oversize the string gauge for fear of the
wooden timbers giving way and the whole instrument folding
up -- explosively.  Also, these are never tuned to A-440.  I usually
only need to match the tuning on the bells, but without knowing I tune
to A-435.  Some were tuned even lower originally.

D.L. Bullock    St. Louis
www.thepianoworld.com