Tail-heavy is nice for fuel burn, and should be what all load planners strive for.............................re: SMTmember.
I flew many years in a sailplane and its performance was much more enhanced when I arranged for an aft CG. As a matter of fact, my elevator position was neutral in the 60-70 kn speed region, which helps to reduce drag. The L/D is positively enhanced and that is what it is all about in cross country flying.
Incidentally; the spin tendency did not change due to the built in docility of the wing's design. But...............when it did spin (on my input) it became a scary machine with a nose down attitude almost vertical ! Recovery always was standard and within 400 ft (even with half water ballast). All the more reason to keep the speed up below 1000 ft circuit height !