Its built from the Royal kit and is stock except for the addition of Springair retracts. The Royal kit is also a "builder's kit." The fuse is constructed like a model ship. It has an internal structure of formers and keels and is planked with balsa strips that you have to cut yourself. I built a jig to mount the fuselage structure on while I planked it. The result is not unlike an aluminum bat - light, strong, and completely resistant to removing any unplanned twists. The wing is a built-up structure that is completely sheeted. Then notches are cut out where the nacelles go, revealing the internal structure that they key into. Each nacelle (4!) is built like a mini fuselage. There are 6 blocks around each nacelle that fair it into the wing. There is also about 10 blocks on the fuselage to generate some of the more complex shapes. I hollowed all of these blocks out to reduce weight.
The retracts are mounted in the inboard nacelles and are mounted at 90 degrees from the way they usually are used. This causes the wheel to retract forward into the nacelle as the real one did. I have a restrictor on the line so they retract slowly. The retracts work great, but since they are mounted this way, a lot of stress is put on the mechanism that it wasn't designed for. The result is that they need adjustment after every landing. Also, the wheels take up a good portion of the inboard nacelles, limiting the fuel tank sizes to 4 oz each. It still flys about 6 minutes with these feeding the OS .25 FP engines which is enough for me.
The entire model was fiberglassed using 0.5 oz cloth and Envirotex as Dan Parsons suggests. Then it was painted with Plasticote Automotive primer and Pactra paints. Then over 100 decals were applied and the whole thing covered with a stain clear coat. I think the finish added about 12-14 ozs to the overall weight of 12 lbs. This gives it a wing loading of 39 oz/sq. foot, and it doesn't have flaps.
After I got the initial trim problems worked out (the engines needed about 4 degrees of down thrust each), it actually flys very well. It is FAST! It also doesn't like to be slowed down too much and the stalls have a very well defined break. Once you get used to that, everything is fine. I've flown it about 20 times so far and it will roll and loop, but that's not very scale. I've never spun it and the first time I do will probably be the last. I just take it up and fly around in circles with the gear up and down, throw in a roll or two, and land. That's usually enough to get a round of applause from the gathered crowd.
My biggest gripe about the plane is that its just a little too small. Its not IMAA legal because the wingspan is 78", although I've been asked to fly it at every IMAA flyin I've taken it to. However, if it was about 84", it would probably only be about 1 lb heavier and could still fly very well on the 4 .25 engines, but it would have more wing area to help carry the weight better as well as being officially IMAA legal.
Oh, and by the way, I have never lost an engine...yet...