Using the Tummy Shield does take a few extra inches of seat belt webbing. If you are already using the extent of the seat belt length, you may need to get a seat belt extender to be able to use the Tummy Shield.
Federal standards that specify the length of auto seat belts date back four decades and only require that seat belts accommodate a 215-pound man. When the National Highway Traffic Safety Administration considered changing the rules in 2003, it estimated that more than 38 million people, or 19 percent of the total U.S. population, were larger than the seat belt requirements. The NHTSA decided not to revise its standards since most top manufacturers including Ford Motor Co., General Motors Corp., Chrysler LLC, Nissan Motor Co. and Honda Motor Co. have seat belts that are longer than required. The companies each provide an average of 18-20 inches of extra belt length, more than enough to accommodate the largest percentage of  drivers.
Many of those manufacturers also have seat belt extensions or longer belts that can be purchased or installed at dealerships. Some offer extensions for free. Several foreign brands, such as Honda, BMW, Hyundai, Mercedes-Benz and Porsche, do not provide seat belt extenders. Extensions have to be used carefully because they can be hazardous if used by passengers who are too small, said Phil Haseltine, president of the Washington, D.C.-based Automotive Coalition for Traffic Safety. According to the NHTSA, an incorrectly sized seat belt extender could fail to provide upper body restraint and may pull the lap belt onto the  abdomen during a front impact, possibly leading to internal injury.