You should be fine with using just your DL with the initial there. What I do is use my GE/Nexus card as my ID for TSA anyways. TSA doesn't need to know my address and I have had instances where I didn't get PreCheck (back when international flights didn't qualify) and a few other instances where the TSO saw my GE card and sent me to the the Precheck line or gave me PreCheck lite if it exists at that portal. This isn't a guarantee of that service but it has happened to em.