Once you get used to the size Campism, you won't notice it much.
When Lady Shadetree and I first rolled into a parking lot that first week we owned our E350, we just looked at each other and giggled.
"This thing is huge" she said.
"It's embarrassing to have this much room for just the two of us" I replied.
We got used to it. Every time we are on the freeway in the van though she always comments how comfortable it is to travel in. Have fun planning your build. Get the mechanics squared away and start on the fun stuff. Good luck!