Indeed, LPG tanks are made to be be safe. The car can have a massive rear end impact where the rear end crumples heavily to the point that the car is a total write off, even so the LPG tank will remain intake. The petrol tanks stand much greater chance of rupturing than the LPG tanks. Most petrol tanks these days are made from plastic.
Even in case of a vehicle fire, a petrol tank will explode, whereas a (properly fitted) LPG tank will vent fuel at a controlled rate instead.
Rest assured you are safe.
@Metalnkey Did you have the install done and if so what size tank did you have installed in the end ?