My 2-cents: remember that you can only add circuits of equal value arithmetically. A 5 amp paired with another 5 amp gives you 10 amps. A 5 amp paired with a 15 amp gives you 10 amps. Two 15-amps together gives you 30 amps. Their website had this wrong initially (e.g. a 5-amp + 15-amp = 20-amp), but they claim to have fixed this.
Going on 2 years with my PDM60 - no problems.
'05 BMW 1200GS
'09 Honda CRF230
'10 Yamaha TW200