"The new Thor Super C puts out 300 hp but torque is 660. I can tell you which one I'd rather have under the hood of my E450 - and it is NOT the V10. Don't know why they shy away from putting the 363 hp version in the C. It can use it IMO. "
The answer to this question is simple: The three valve heads don't fit between the front seats of the van.
I notice that there a not any responses from an actual owner yet, makes me wonday how many have been sold and made. I was considering buying one when I bought my Pallazo but never could find one for sale. I really liked the short rear overhand of the F550 chassis and the increased towing capacity. This coach is really rated to pull over 10,000lbs. The Palazzo is transmission limited in its ratings to only 5,000lbs or thereabouts. I do wonder if the Ford transmission is really stronger than the Allison 2100 of if Allison is just being conservative compared to Ford.
In response to the op's question, I am seeing about 12mpg from my Palazzo that is much heavier. I would expect the Super C to do at least as well. If you plan to use the generator much I think that you will like the diesel genny much better too. The larger fuel and water tanks on the F550 chassis (compared with the E450) are nice too.