That's not how it works. Durability and dps go hand in hand, the lmg grenadiers losing 2 models means still having most its dps, while the dps of 4 men grenadiers drops drastically with 2 models lost. As the dps drops, the enemy retains much better dps, so your durability is is actually lower.
thats not how durability works. durability is the amount of punishment a squad can take, not how quickly fights end.
5 men mean more health, but also more targets, which spreads out damage, meaning less odds of a model being burst down. but additionally, how much pray tell dopes tthe lmg42 protect against mortars? snipers? tanks? mines?
side note, you are describing the lmg42 exactly for its purpose. centralized DPS to offset the small squad size. this approach was in contrast to the soviet, who instead of centralized dps had additional durability. outfight or outlast. dont expect both on a 240mp unit let alone one that starts with a snare....