The entities that are "smashable" by default inlcude a little extra in their fpe
;statistics
strength = 25
explodable = 0
debrisshape = 1
afaik there is only a limited number (5?) of different
debrisshape available so you'll either have to stick with entities that are covered by this (and no, I don't know exactly which or what so pretty please experiment yourself a bit)or create your own debris (and no, I don't know exactly how to do that either).
In case you find my grammar and spelling weird ---> native German speaker ^^