[TippetsTX]

I have similar rules in my game...

Melee weapons do +1 damage for every three points over the minimum required ST or +2 damage if the weapon is two-handed.

Using two-handed weapons in one hand requires ST to be at least five points over the required value, but I agree that shouldn't work unless the character is considerably bigger than a typical human (larger grip). I may just replace this with rules for larger-scale weapons.

Armor also has minimum ST requirements in my game and I reduce the MA penalty by 1 for every five points over that figure.

I will typically let characters start chucking heavy furniture around starting at 16 ST. Damage will vary, however, based on the ST used, object size and material.