A fellow researcher located this book on Google books: "Loyalists in the Southern Campaign of the Revolutionary War: Official rolls" and sent me a link. Listed on page 24 of the Muster, Capt Robt Pearis' Company, SC Royalists, Camden, SC, 24 Feb 1781, 60 days inclusive, 24 Feb - 24 Apr 1781: Privates Edward and Owen Sizemore. Under remarks: deserted 19 Apr 1781. I only looked at the first 35 pages and these are the only Sizemores I saw.
Evelyn Leslie