I recently had a need to splice two round leather belts of the same
length with a "soft" splice for my Mortier key frame.  I was afraid
using a wire staple would tear-up my drive wheel which was fabricated
from soft laminated mason board.  So far, my splices have held.

Using an awl, a hole was worked through each end of the splice close to
the end.  While the ends were held together, I then threaded heavy duty
synthetic thread through the holes several times, drawing the ends of
the  belt together.  I then arranged a knot to be hidden in one of the
holes, having first soaked the thread in super glue.  I then trimmed
the exposed ends of thread and applied super glue to the exposed
multiple loops of thread across the butted ends.

Dick Leis