ken,
While it is true, you can get some great buys in this market on used gear, you can also get some great deals on a custom build too.
I am a big fan of building it your way. I know what I want and it just seems to me that if I am going to spend this much money, I am going to get it done the way I want it done.
In your case, the dead room can make or break the coach. If you have the means, ($$) I would seriously consider having a coach made to your specs and incorporate the head room as well as the rest of the features you want or need. This is especially true if it is something you plan on keeping for many years to come. You will likely be happier in the long run with your truck rather than someone elses ideas.
I feel that is one of the best features of the HDT option vs the Stock RV.
A used HDT and a good builder in this market can create a pretty compelling arguments for the best value.
Just my thoughts on the topic...
Rad