The Bounder is a lot bigger RV than the one in the add , it is very likely already been downplated to 7.5 ton as that is what most gas engined RV s are sold into that market , the FREDs or pushers are usually full HGV licence as they can weigh over 7.5 unladen . The bigger RVs are a a bit restrictive , on site access , or road suitability , but the one in the add is much less of a problem . I used to own a RV (largest allowed on UK roads) , so am well aware of down sides, the fuel consumption on the one in add is around 12mpg , but majority operate on LPG , which makes them a lot more economic in the long run , the fuel consumption , even on petrol is a factor only if you move around a lot . The thing to watch on these vehicles is damp , especially if roof hasn't been looked after . They are ideal for a semi mobile living experience tho . JMHO