I have seen some racers use silicone caulk to glue their 4S LiPo on the chassis of 1/8 cars and remove the battery tray... there are many brands of cars that use velcro straps which tend to generate too much flex and cause premature damage to hard case LiPo's so gluing the battery to the chassis mitigates this issue, plus the silicone acts as an extra layer of flex to help increase grip.