I have a 1951 XK120 OTS. It has a Black Mohair Tonneau Cover that I have to steam to get it to fit back on the car after winter. The steam works well with the fabric and there are no marks left. The secret of course is to apply the heat or steam slowly and to the surrounding area as well. In the case of a convertible top, I would suggest applying the heat / steam on the underside as well.