[aerohead]

The drag reported is for the images as depicted,and the only canopy with 'fillets' is the top image with its reflexed contour.The solar teams might place the canopy within the 1st 30% of body length where the boundary layer was minimal in thickness and they'd have a shot at laminar boundary layer there.
The fillet would address 'junction' drag and associated hook vortices which can form at this intersection between canopy and body.If you look at the canopy for the 1957 MG EX 181 Cd 0.12 land speed record car,you'll notice the fillets at the base of the canopy to address the hook-vortice junction drag.
Junction drag is addressed by Tamai in a different section and he cites Hoerner's work in this area.
----------------------------------------------------------------------------The time period would be from before 1995,when Tamai and team mates were conducting wind tunnel tests to determine their MIT plan of attack on drag.