my mom has a ton of antique-ish molas that she says aren't washable- have you tried to wash yours? are any of yours older?
My molas are all pretty brand spanking new and no I haven't tried to wash them. I'm not a big quilt washer and don't really plan on washing it. I always use a top sheet underneath quilts and try to keep bare asses off them, and they stay clean enough for me.
If I were dealing with some antique molas, I probably wouldn't make a functioning quilt. But then again, buddha sez permanence is an illusion. If you have to wash them, I'd go super gentle hand wash style. A washing machine would be more like a wood chipper on them.
As for the size of them, they vary from 16" to 18" wide. I measured another quilt of mine to figure out how big the final product should be, subtracted inches for all the borders around the squares and then divided by 3 to figure out how big each square should be. I think each mola plus the bright frame around them were something like 25" or 27" square.