Do not apply the 'STR Min Cannot Add/Subtract Damage' limit to items built with powers to do not allow STR to add such damage in the first place. RKA for firearms is the most common example.
When applied to Hand-to-Hand Attack, STR Min does not limit the damage to 2x that of the weapon nor does it use the STR Min and the weapon damage as the baseline for adding damage. Instead the HtH Damage applies it's bonus as normal to a characters STR Damage.
The STR Min only specifies the minimum STR needed to effectively use the weapon. The characters suffers a -1 OCV and -1 DCV for every point under the requirement.
Examples:
A STR 10 character picks up a club that gives +2d6 HtH Damage and has a STR Min of 5. He does 2 + 2 or 4d6 using his normal OCV and DCV values..
A STR 5 character picks up a staff that gives +2d6 HtH Damage, +1 OCV and has a STR Min of 10. He does 1 + 2 or 3d6 damage with a +0 OCV (the +1 for the staff counters the -1 OCV for being under the STR Min) and a -1 DCV.