hmm what do other do? well others do everything! for example in my mom's old house she has the easy way out: the beams are just boxes made of 1x material. on one house i worked on they had 18"x12" solid beams. so the whole structure had to be modified. hmmm the problem you face is the proportionsing of the beams. now i dunno what your looking for. for example will the "beams" be just a 2x applied board? or do you want them a little beefier?

I am figuring on making the beams out of 1X material and am wondering what would be a good size for the "boxes" like what you described in your moms old house. I have 5" wide X 1" pine that I would like to use but am concerned that they wont make a big enough beam I can get wider wood if 5" would look to undersized.