We could do with rather more specific info than you have posted
Sluggish to respond to controls or sluggish in performance I wonder? Weight?
In the end only three things give bad handling with an established type - a wrong shape, a wrong CG and wrong controls.
A set of weight and balance checks that are repeatable must be your first aim. The DC3 is not enhanced by an extended aft CG. If the eventual mission you want to use the aircraft for will allow you to keep the CG fairly well forward it would be sensible to do so.