I am wanting to weave some fabric for a lightweight summer top in 20/2 cotton in a Wall of Troy (twill) pattern but am confused about the sett. Jane's Master Sett Chart only goes to 16/2 but says 30 epi for a nice drapey twill. Handwoven says 36 for plain weave and 48 for twill and Schatt say 32-36 for twill. I know I will get my hand smacked for saying this, but at 30-48 epi I don't want to get it wrong and have to resley it all. Any help would be greatly appreciated. It is my first time weaving with anything so fine.

You could try making a test warp that is only 1 yard or so long and 8 to 10 inches wide. That would save you a lot of time resleying. Then you could wash the samples and see which you would prefer for your final project. Even what seems like a small change in the sett can make a big difference in the drape and feel of the cloth.