I have built a Ofna Lx2e, it's gonna be used for minimal club racing, or practice days and on our personal track. I see lipo advise all over, types, ect. I have a castle sidewinder 8 system installed, I'm looking at turnigy 4s 20/30c lipos or something close. What c rating can i get decent use out of? My manual says nothing less than 40c but I see a lot of people using turnigy 20c. Any help would be appreciated.

The Castle manual states to use LiPo packs of at least 5000mah and 30C or a pack that can burst at 125amps and sustain a 90amp draw. If you use a very well engineered pack you could drop down to a 25C.If you change gearing then you may need an even larger pack.
I would not be using any Turnigy pack or any pack from Hobbyk*ng.

Go with the Wolfpack Lipo packs. Tower hobbies. hard shell good quality cells.

There is a reason for suggestions in manuals. With the heavier 1:8 scale buggies/truggies I used LiPo packs with nothing less than 40C discharge rate. I destroyed six 25C packs in a very short amount of time while putting them to the test in a 1:8 truggy. Extremely puffed cases (split open); desoldered battery cable inputs; too hot to touch cases...I had everything bad happen when using under powered LiPos. After changing to 40C packs...more efficient power delivery to the ESC. No more LiPo packs put into the battery graveyard.