I know from a historical accuracy view point that most commerical patterns have flaws. It's really more about how to make a Halloween costume that looks medieval than something that would pass in the SCA.

Not that I have any good costuming links off of the top of my head.

BTW - HAve you ever heard of Gerald of Ipsley or Robert of Cold Castle? They are from Calontir (Missouri). They came to our event on Saturday and they are just amazing.