I think we forgot to mention something else too...

ANY fast charge heats the battery.

Without any airflow ... the battery can't cool off. The foam is a great insulator... like a thermal blanket. Keeps the batterys warm and toasty. (so they can fry easier.)

I never charge at above C/4 with the battery in the airplane.

I now never charge the TX battery while it is in the radio AT ALL! (I used to charge with the Wall-Wart leaving hte battery in the TX... had one vent. THAT was a mess.)