I was at the Arlington 2012 fly-in and saw this RV-6, among many other RVs. Initially only noticed the extra long nose, which I presumed (correctly) to contain an O-540 like a Harmon Rocket.
Closer inspection revealed that the canopy was extra tall. On my RV-6, the top of the canopy does not rise much higher than the top of the windscreen. But this one had a lot more bulge to it. I often wish that my RV-6 had better visibility over the nose, so I started to wonder how this guy got that extra height out of his canopy.
The builder showed up and gave me (and some other interested people) a tour of his airplane. When he opened the canopy, it became clear that the luggage section was much longer than on a normal RV-6. Clearly the fuselage had been stretched!
Not only had the fuselage been stretched, but also, two aft-facing seats had been added to the back. They're small seats, for kids, their backs going against the backs of the front seats. The seat bottoms can fold up to go flat against the backs of the front seats (as shown here). The bulkhead (not shown here) has holes so that the backseaters' legs can go into the tail cone.
The stretch becomes obvious when you look at the region where the trailing edge of the wing meets the fuselage. In the cockpit region, the fuselage has a rectangular cross-section. Where the flap meets the fuselage, the edge of the rectangle starts tapering and rounding into the tail cone. The fuselage was stretched in this region where it has a straightforward rectangular cross-section. The spot where the rectangle corner starts becoming more rounded has been moved aft and is now about a foot aft of the flap trailing edge. So this foot of extra edge along the bottom of the airplane, which you see here, is the stretch. How did the canopy stretch so much further back? Well, you can see here that the piece of metal that arches along the aft edge of the canopy is a little wider than usual, so that gets you a few extra inches. The remaining extra inches come from the canopy itself. Apparently when it comes out of the mold, the canopy has a few extra inches sticking out to each side, and that extra material gets cut off before the canopy is shipped. This builder got in touch with the manufacturer and managed to get his hands on a canopy with all the extra material out of the mold, un-cut. This gave him several extra inches of canopy, enough (along with the wider metal arch) to bridge the space from the windscreen to the tail cone. It also gave him an extra couple inches of height! Very cool.
Here's the info that was taped to the prop, with the details of the builder, year, weights, etc. The registration is C-GZII.