If somehow Becnals cranks are really threaded 'the wrong way round', there's a fairly easy solution that doesn't involve disassembling pedals. Find a set of screw taps (left and right) with the proper measurements for pedal spindles. Then cut a new thread in both cranks (now the proper way around) and mount the pedals. This is a solution an engineer whom I know and trust uses quite regularly. He claims there is way enough "meat" (as we call this in Dutch) in a crankset to 'countercut' these threads and still properly hold the pedal in place. If you feel the need, apply some Loctite when mounting the pedals.

Just my 2 cents worth.