When I first tried to put the spindle through the bearing I was holding each in my hands which was not very stable. So I tried again after first threading the external bearings onto the bike and then carefully tapping the crank arm and spindle into the bearing using a mallet. After over-coming the initial resistance, it slide right through both bearings and out the other side without a problem except for the fact that the spindle is too short for use with external bearings, which I knew this may be a possibility, but I wanted to be absolutely sure I could not use my current carbon crankset on the new bike in the interest of saving money.
So now I either wait for the SRAM dub system to be available or go with a current model SRAM or Raceface alloy crankset.
How often do you change and swap cranks? The Dub system is nice in principle but I wouldn’t wait for it to come out. FSA has had a similar system (modular) for the last two years as well, you could contact them.