I slightly disagree with Udo. The best result, in my opinion, having
flown '24's in all the combinations, is the leading edge mod and
improved winglets together give the best total result.
I never saw any deterioration of glide with leading edge mod and did
see improvement in gust sensitivity.
He is very much correct that winglet is most important as it keps the
tip working and aileron effective down to a speed where overall drag on
the airfoil begins to rise due to separation.
'24 is a great glider, I'd still have it today if Gerhard had not made
a little bit better glider in the "28.
Good Luck UH