XR- The battery securing method has long been an issue with some for 12th scale cars. However let's remember that NO rc car is immune to a DNF on the battery ejection front. In the past 3.5yrs i have seen my share of TC's out of a race with the batteries hanging out of the car also.

The quick answer is that we use a form of strapping tape that is much stronger but thinner and easier to work with than normal, super sticky, wide strapping tape. Yokomo and Tamiya sell it as well as a company called Racer's Choice and also a company whose name escapes me (something like RC Racers or Racing Products-it's black and thin). I use the latter, it's black and very strong but light weight and pretty sticky. You could also probably make a Corally like hold down for a 12L3/Six Pack without too much hassle but you will add a little more weight compared to strapping tape.

The reality with all of this is that other forms of securing batteries have their ptfall(s) as well. The "O" rings used on some cars have popped off in severe enough crashes and the lock down method can bow the chassis plate inducing tweak and the batteries STILL can come out.

Try either one of the above listed battery strapping tapes or use a post and drill a hole in the chassis plate and replicate the Corally hold down method. Either way in most cases you will be fine.