There are various mast-up facilities on Lake Travis, and it's a good-sized lake too. I am personally familiar with Highland Lakes Marina at Volente Beach, and with the Austin Yacht Club. HLM has a (grassy) cat beach that is quite nice at certain lake levels, and always serviceable. The Yacht Club has a paved lot with "dry slips" while HLM has a grass lawn with some paved and some rock driveways. Good luck.