First off let me make one thing clear - we bought the most trailer we thought the car could handle for the short term, with the plan to get a larger vehicle for towing in the future (Touareg). Short term may stretch to a few years depending on how life happens....
Something most people miss when looking at travel trailers is aerodynamics. The Egg Camper is designed by a former(?) pilot and a big point for him is how smoothly it tows. He had sold several to people with Subarus (Impreza no less). It's big and wind will effect it but not as much as a stick frame camper. When I came back from the TDI fest we hit nasty weather from the hurricane going up the east coast. Only pucker moments were from hydro planing as it was raining so heavily (we should have been stopped anyway it was so bad).
I have RC1+ or whatever he called it on my PD Golf. It feels stronger than the CR cars I drive at work. The wagon would probably tow better - longer for stability and better gearing for load. I looked up load rating for my model in UK - over 3000lbs. But then I also added the airbags to my rear springs from Summit Racing, so it doesn't sag.
I pulled a Uhaul 2500 miles with that car stock and that weighed about 2800lbs. It handles the weight fine, though stock it would struggle on hills. Stopping always felt sure footed and not over powered by the load.
I have the all electric Egg (all he is building when I bought) so there is no propane tanks. I have a front bath on mine. The fresh water tank is over the axle but the grey/black water tank is up front under the bath. To be honest I usually keep the fresh water tank full in case we have to stop some where w/o hook ups and just move larger items in the camper for balance. We have a generator that I move to the back so the tongue weight isn't too high. You definitely feel the camper back there but I don't think the weight is that close to the limit that a few pounds of supplies or belongings is going to push it over the limit. BIG CEVAT - load carefully!!
Side note - I think Casita is heavier for the same size because of full fiberglass shell (underneath), I don't know about Scamp. Both look like they have regular wood cabinets - the Egg has its cabinets molded right out of fiber glass. Also more minimalist interior.
BTW - I get 28MPG at 65 MPH, I can get it up to 35 MPG below 60 (57 seemed best)MPH.
Jason