Dude, I'll tell you in the simplest way I can: Get stronger, and your body and its physiology will do the rest. If physiology tells your body to add more mass, it will; otherwise, you will lose weight. It's that easy.
Just train hard, eat plenty of protein, good fats, and complex carbohydrates. Stay away from sugars and trans fats. Your body will do it alone.
thanks a lot Robert, you and SouthernLifter appear to be absolutely correct.
Meanwhile the weight on the bar keeps going up (1x5 DL was 12.5 kg more this morning, now at 152.5 kg [335 pounds], only 27.5 kg more than my 3 sets of squats this morning) and my bodyweight seems to have stopped rising (without me changing anything about my diet), more or less.
The 405 lb Deadlift is slowly coming into view, which is my next DL milestone per se.
Thanks again for everyone's responses.