I did the same to my SLR saddle. Some advice: make sure the glue isn’t too wet when you put on the alcantara or else it will soak through and the finish will be poor. And keep in mind that alcantara, due to its limited felxibility, is more difficult to drape over round shapes than leather, for instance. This means you have to be economical with the limited amount of flex the material affords and use it evenly. If you pre-stretch the material too much while draping it over the top of the saddle, the edges won’t be smooth since the material will overlap rather than stretch. Also, the material is very thin so any imperfections under the alcantara will show. That’s why I’d recommend practising on a test saddle to get a better feeling for the characteristics of the material.