Casey advocates that from a strength standpoint. It has nothing to do with the epoxy resin being used. Mat has littlr strength but is easily shaped (faired). Rove on rove is weak without mat in between. Cloth with mat gives you strength, flexibility in application, and shaping ability. Much depends on the size of repair, with cloth being the easiest and strongest to work with on small areas. West system has free literature that is quite good on the subject; between them and Casey you'll not go too far wrong.