Putting Lipos on a glow trainer is like putting a gold spinning rims on a Yugo. If you want, you can make the switch to Li-Ions this early, but a $10 NiMH pack is all you would lose if you waited until you were flying planes which might benefit from litiums. Frankly, by then there will be a new battery technology available. They (LiPos) are occasionally used to power a large servo, like a seiko, seperately from the rest of the servos in a larger plane.

If you use any pack over 6V, you will need a regulator....again, not a benefit for a trainer.

The truth is, you cannot quick-charge any type of lithium battery. They take an hour...period. With your NiMh or NiCD pack, you can charge at much higher rates. Lipos are rarely used for RX applications in fuel-powered planes. Just no benefit from doing so.

I have charged NiMH and NiCD at as high as 5C...you just need to keep an eye on them. They can over-heat.