tdwise,

The short answer is that fixed slats will increase drag for high speed, low angle of attack flight. Now for the longer answer. Slats give higher lift, usually for takeoff and landing, by allowing the wing to operate at higher angle of attack without stalling. If you imagine the airfoil section as the slat is deployed, you can see that it does two things. It increases camber near the leading edge, and it decreases the angle of attack of the wing, if you assume that flaps are not deployed at the same time. For high-speed flight, you don't need that added camber; it will only add drag. The bigger problem would be if the decrease in angle of attack actually pushed you below the zero-lift angle ( ie. the wing would generate downforce along the part of the span with the slat ). This would be pretty bad. I don't know what the fully deployed slat looks like on the FS A-10, but I would guess that it moves pretty far, and is visually obvious. If this is true, and you are after a scale look, you might want to make it a working slat, so you can retract it for normal flight. If you are happy with a smaller deflection, then it wouldn't be as big a deal. In any case, fixed position slats will have some drag penalty at high speed. It would probably be a fair amount of effort to build working slats that give a really smooth surface when they are retracted, but you are already doing fowler flaps, so you probably don't mind that.

I wouldn't break you back or compromise scale appearance for the Hoerner tips, I doubt you will notice much benefit from them. If it's handy, I'd love to see pictures of your wing details when you get that far.

Good luck,

banktoturn