Max--Basically with the 3300's you should charge them at 5 amps with your peak set at about .05 (this depends on the charger). Ultimately you would like those packs to get up to about 125 degrees, but no higher than 130 at the time they peak (pick up one of those little temp gauges for measuring this). It's a good idea to charge at 5 amps when using a mod motor since your power comes from the motor anyway. Plus you want to be sure that you make time in a race, so charging at a higher amperage won't help you. If you were running stock, then you might bump it up to 6 amp charge rate, but for mod go with 5 amps. Your peak detection will vary depending on many different things such as ambient temp (higher peak if cold and lower if hot), state of battery at beginning of charge (should be discharged at start), etc. The one good thing about the 3300's is that they are a proven cell and can take almost any abuse they are subjected to....
Hope this helps you with your charging and feel free to shoot me a PM any time you have a question concerning batteries.....
Keith Whisler--Slingshot Batteries