DYI hole in the middle hood tips if you don’t have one to copy:
About a 28-29″ circumfrence hole is good.
Make the hood about 8″ tall in the area from chin to edge so there is plenty of material to tie off in shelter mode and for seam allowance.
Make the hood base circumfrence 2″ more (30″) than than the hole cut in the poncho so that when sewing it in it will fit…the hood edge part will follow a wider circumfrence than the hood hole after seam allowance. About .75″ will get used up making the chin seam before sewing it into the hole in the big sheet.
Layout small sharpie dots at 90,180, 270 degrees around the hood hole and the hood edge so that when sewing if it is not perfect you can see which part to stretch a little as you sew around.
Offset hood hole 6-10″ to the front so it will have enough extra in back to cover a pack.
Hem Edges Tip: Tripple roll edge hem and make it 1/2-3/4 inches wide(not the tiny 1/4″ somethimes used. The wider hew makes it so edge reinforcemnts are not really need on a small silnylon tarp like a poncho.
Hood Pattern Tip: Cheap 2mil painters plastic and scotch tape is quick and cheap when trying to get the pattern you like.
have fun!