Anyone familiar with post and beam straw bale house????

i want to build a small post and beam strawbale house 22x45. i have read i can build the walls with 4 by4's every8 ft. besides at the doors and windows. i want high ceilings for lofts at each end. the floor in the lofts will help hold the outer walls in place, but in the center there will be about 23 ft. open and im worried about outward pressure from the ceilings in this middle section. can i put a couple of 6 by 6 beams across to help keep the walls from deflecting outward from the roof pressure? roof will be lightweight premanufactured metal truss with colored metal roof. so the roof weight will be much less. please help with any info on this. thanks