RE: cheap reciever, fuel tank battery e.t.c protection
G'day Foamy,
To check if the foam you are using is any good, place it between you thumb & forefinger & squeeze, if you can flatten it so you two fingers close together, it is NO Good.
The RX or battery that you have wrapped in that foam, in a sudden stop will compress the foam, the same as your fingers did, so find a rubber type foam that has a bit more guts & protect your RX & battery.