i too am in texas with a similar dilema. ive been sailing a 16 for 10+yrs without registration. the old rule was if it was sail powered no numbers needed. this was changed in the early 90s. most sailboats like ours were never registered. i called the austin tpw office and told them that i had bought this boat in 1990 and never sought to register it. she said to fill out an application for title and registration. my boat has a serial number and that is what yours is missing. they cant issue a title without a serial number. she said it was no big deal as far as getting it registered and titled but to put in a letter explaining the circumstances. they are more interested in collecting the fees than anything else. my hull serial number in nothing more than an engraved number. as old as your boat is i think you could get away with any digit serial number as long as it is prior to 92. i cant imagine they call hobie to verify and the odds that "actual" boat is registered in texas is between slim and none. bottom line is create a serial number to put on the application for title and state that is was never titled because of the pervious law. expect to pay sales tax and registration which should be in the 6% range. last alternative is to "build" a boat. get reciepts to show parts and equipment. if you can get to 300 or so they can inspect it and issue it a serial number.