I've been getting good crimps on the crimp sleeves just using a cheap crimper. The first crimp makes the sleeve into a deep V shape, then the second one folds further closing the V shape super tight. I've been just doing two into one crimps though.
THE LIPO RULES. NEVER ABOVE 4.3V NEVER BELOW 2.7V DON'T PUNCTURE
Ideal charging /discharging range for Lipo, 3.65v minimum 4.1v maximum
See battery technology section, FAQ thread at the top of the page for lipo noob info.