As always, the one that best matches the needs of your particular design. If you're going to use trailing-edge control surfaces on a tailless design like the Verhees Delta, then a positive pitching-moment airfoil will be necessary. How much positive will depend on the particulars of your specific configuration and the mission profile.what airfoil would be appropiate?' A zero negativ pitch foil?
I was just having a re-read of the 'Slow Delta Wings' thread and in this post Deskpilot says some DD had fabric covered undersides. Maybe that's the answer?
Full-scale pusher deltas are fraught with problems unfortunately.I'm kind of stuck on the notion of a prone pilot electric pusher delta like so. The proportions are a bit off since this was just a quick and dirty design but it gets the idea across.