300 lbs (he's down to about 230 now) when he bought his Hoss Deluxe 3 years ago. He rides pretty agressively and breaks components. But the frame is still ROCK solid. I think it'll handle you Stepdad no problem.
Kona has named a frame for clydes, which seems no different than a Stuff or Scab( I think) frame.
If youre step dad wants to support his LBS, find out if they sell Specilized, as the Hardrock pro is also a bombproof frame