Team Fab:
The only modification we had on the DI-2 was to substitute a NMH battery inside stoker seatpost for the Shim. battery pack.
Worked great for 1360 miles before having to recharge the unit. Worked good for another 300+ miles before becoming problematic and finally failing on a hill climb. No warning from the light system indicating any impending battery issue.
Fortunately we did not pay $3,600 for the DI-2 setup as we were being test dummies.