I'm planning heirloom pillowcases - doubleweave so there aren't any seams on the sides.  Probably 3/1 twill.

I'm considering 40/2 warp and weft or 20/1 warp and weft.

Would the singles be harder to manage?  I live in Oregon so humidity is pretty much guarenteed.

Any thoughts?  40/2 warp and 20/1 weft?  Would be unbalanced but might look okay.

Thanks.  Pat Z.