Technically, affiliates cannot get shorter assigned SFI Gateway Website addresses. However, you can get your own domain name (e.g. MyName.com) and set it up to automatically redirect to the SFI Gateway of your choice. In other words, you could advertise www.MyName.com, but traffic would automatically redirect to the Gateway you wanted to use. This is a very common practice and very easily set up.
In fact, you can purchase a Lifetime Custom Prestige Domain and redirect it to your SFI Gateway in minutes. Learn more HERE.