i bought a new h17 sail last year and it had the h o b i e logo running vertical on it. i tried several things to remove the sail numbers and letters. acetone doesnt work at all and probably isnt good for the sail. there is that sticker remover you can get from the auto parts stores that works but who knows what is does to the long term life of the sail. since you have an old sail this probably isnt an issue. what i found that works is- peel off the existing decal, which will leave the sticky stuff behind, use an old cotton sock and just work it off in circles until it balls up in the sock. this is very labor intensive and will leave your finger tips raw! just go slow. i did just one letter a day. anyway, #100 is a cool number, maybe you should be happy with that?