Without a response, I can see it quickly turning into a holding tank lynch mob!
Unlike some companies, we like to use our product and I will agree that our family of four will struggle with the holding tank sizes when camping off the grid. I have learned to pack a 5 gallon colapsable water tank so I can refill the water tank. I also have a bucket to drain off the grey water tank. The black tank has not yet been a problem as we all use it....but realize it is not easily drained, so we are resourceful. This will not be a good enough answer for all so, I will get into details.....
When designing the trailers, there are many areas of concern.
It starts with the frame construction. There are crossmembers in the frame to support the floor which the tank must fit between. This limits size. The tank can only be so deep in order to maintain road clearance which also limits size. The tank can only be so long to leave room for the inlet pipes. Then we add in features which you will appreciate while towing such as keeping the tank as tight a possible to the axle. Not only does this reduce the vulnerablilty of the tank from curbs and such, it also helps balance the weight. This tank placement is one of the factors in which we received a 4 star rating from the RV Consumer Group. Many if not most RV trailers will have the 4000ish gallon fresh water tank under the bed a the front of the trailer and the 3500ish gallon grey tank under the bathroom at the rear of the trailer (generalizing here). Looks great on the lot because you can be self contained for 3 months! You leave home with the trailer loaded for your trip and the front wheels of the truck in the air with all that hitch weight. When you come home...hitch is lighter but no the trailer is all over the place because the water is in the back...or at least until you hit the sani. Tongue and cheek obviously... but accurate. Escape owners do not worry about water transfer as both tanks strattle the axle.
Early models of the Escape had an 8 gallon black tank and a 14 gallon grey tank. New customers were quite happy with the new tank sizes of 14 gal black and 20.5 gal grey. I agree, another 5-10 gallons would be great, but at what cost
? Everyone would still empty 50 gallons of water on a weekend trip if it was there and still say...why can't that Reace guy put in a larger tank?
I hear ya and I'm always looking for solutions.....I even fell asleep late one night on a creeper under a trailer while studying it for hours! ...(NO KIDDING