I think this is what you do:
First, make sure that it uses the PlayerStandardArmor.
The category type might not matter, but I suggest still not setting it to vehicle.
datablock PlayerData(RotBugZombie : PlayerStandardArmor)
{
category = Armor;
The numbers for these should probably be big,
(you don't have to include these)
minImpactSpeed = 160;
speedDamageScale = 100;
I'm not 100% sure this is all right, but it seems like all you need to do.