Krueger Flaps
 

Anyone know why Krueger flaps are generally only found on the inboard section of the wings and then slats on the outboard?

This is a standard JAR ATPL POF question.

Krueger flaps are less aerodynamically efficient than slats, so they stall at a lower angle of attack. (Kruegers decrease stalling angle of attack, whereas slats increase it) Using Kruegers inboard and slats outboard ensures that the wing roots stall before the tips.