If he doesn't like "skinny" jeans he's certainly not going to like 511s.
511s are the roomiest fit I wear nowadays. Worn true to size, unless you have particularly muscular or fat thighs, there is no way I would call these "skinny"; they are not close-fitting below the knee, as they do not taper. They are a mildly slim fit, at best. I wear workboots under them with no problem.
I'd size down quite a bit because i heard these stretch quite a bit.
The 1980's (and KMW in general) are not nearly as bad as you think. There's a unique 'elasticity' to the denim I haven't experienced with other jeans (must be the high denim quality). On a scale of 1 thru 10 (10 being APC and Jean Shop with sometimes +2" waist stretch, 1 being Momotaro or Skull), I'd definitely put these at a five or less.