LPG plant – where to install tank ?

Hello together, have for a couple of months a G500 with which I now would like to have a PrinsVSI Autogas system installed. Now the question arises where with the gas tank. Actually had to have a cylinder tank installed under the vehicle between ladder frame and cardan shaft. The gas retrofitter was up to today quite optimistic and had already ordered the suitable tank (50 liters). Unfortunately the TÜV made us a line through the bill. A gas tank should not be next to the Kardanwell There is even a law for this. Does anyone know that ? Have already seen some vehicles (wrangler …) with which this was installed. Now should a cylinder tank in the trunk on the left wheel box. Shall fit in 70 liters. Where have the LPG drivers had the tank installed among you at the G? Are there better alternatives than the wheel box in the trunk ? Thanks already for every tip !