Yay, more tandem owners, welcome to the family!
Please get some discs on before you try any 'proper' downhills! Our 'dale had V's to start with. We launched her down Eyam Quarry on her first outing in the peaks. Even with the brakes on from the top we were hitting terminal velocity, thankfully the barrier at the bottom was open, otherwise we'd have been toast. We actually caught a motocross bike on one downhill, and that was with the brakes on!!!
The favourites seem to be Hope M4 / Ti6 / V2's or Magura Louise or Gustav.
Happy fettling!!
Rob & Sandy