RE: mega 16/15/4, did i make a mistake?
Yep, the KAN1050s are starting to suffer from severe voltage depression at 15 Amps. Definitely not good for extended runs.
A popular choice for lightning-quick Projetis around here is the /3 on 8 cells, and they're running CP1300 NiCds or 1950 HR4/5FAUP NiMHs. Use 10 of the 1950 HR4/5FAUP cells and your /4 will come alive. Maybe even a 6x6 prop for even better speed.