I had to open up some walls and ceilings, now the man says insulation needs to be brought up to code. Rafters are 2x6 @ 24" o.c. and need to be 2x10's, thinking sistering up the rafters with screws and glue us my best option, past experience tells me 2x4's won't take that many screws down the skinny side, and it would probably crack the rafters. The walls need 2+ inches added, I think if I pre-drill ripped 2x4's I can get away with slapping them right up against the existing 2x4's to furr the wall out to 6".... thoughts, ideas, suggestions from past experience? This is all old growth, 2x's as my house is 70+ years old.