If your pack does not have bumps molded into it, then just cut some lexan strips that are the correct width and servo tape them into place. It works very well.
Team ORCA / ORCA USA / Pro Spec
Serpent America / Team Serpent S411 ERYX / On Point Racing OP12C, S120 / Xceed Products
Hangar 30 / Seattle RC Racers
Fasttrax Racing Series / NORA On Road Series