Foam board swappable fuselage scratch build series is setup like this, the Nutball as a beginner, the FT Flyer as the next step up, then the Delta wing for advance flying.
The FT Flyer (BluDart) is a great intermediate scratch build offering all the ease and fun as the Nutball but offering a nice transition into more aerobatics and aerial maneuvers helping you improve your skills and prepare you for the Delta wing.
One of the best part of all of these wing designs is that they are constructed from inexpensive foam board, so if a wreck does happen, you're only out a dollar or two worth of foam.
Scratch building these foam board planes is a fun way to learn more about RC flight, improving your flying and it's a cheap way to explore your creativity in designing your own airplanes as well as a great way to introduce friends into the RC hobby!
The plans for the FT Flyer are available here:
View attachment FT FLYER SWAPPABLE FINAL.pdf
See how to build the swappable fuselage here:
http://flitetest.com/articles/DeltaScratchBuild