I bought a D 1 repro the other day which has lost some surface seal and is rubbed in a couple of places to the skin. I have used petroleum jelly on similar jackets to good effect years ago which I think Pecard's is based on - although with added oils and waxes. So I went to the Aviation Leathercraft site to buy some and it had this warning. "Caution: This product can be used on our sheepskin jackets and trousers as well as the leather jackets, but please remember that sheepskin is not the same as leather and does have a 'surface' that will wear to a suede-like finish over time. Pecard's can help to preserve the 'leather-like' appearance for longer, but do not use on flaking or rubbed surfaces. If the surface has begun to crack please do not use, as any treatment now will make the surface peel." Has anyone had a problem using it? I thought it was recommended for original Irvins and most of them will be a bit rubbed by now.