Agreed. So Ben my input is to look at using honeycomb aluminum for bulkheads, crush zones, and a safety shell as found in modern cars but without the roof. The head piece to be faired as per Alan Smith's. The main bulkhead behind the back should be able to withstand 3 times the gross weight with the rider. Width is going to be around 26" so length will be 3 to 5 times that. A low nose and a high tail with curved sides seems to be the best for stability to date. By using elliptical bulkheads and conic sections we could avoid the compound curves that are so hard to form. The honeycomb can be used to form curves by making cuts to the inside. See "Successful Composite Techniques" by Keith Noakes for info on cut and fold methods. I have looked at a number of sailplane plans and my favorite is found at
www.vintagesailplaner.com/Sheet1bis-9.pdf - just reduce the drawing view to see the whole sheet. For our purposes end the shell at the #6 bulkhead either as a kammback or taper to a point. Size the shell so that the canopy top comes to the shoulder then form a narrow windscreen and helmet fairing. Given the skill you have shown on your previous project you should do well.