There is nothing wrong with using lighter bullets if it suits the powder. Probably what I would do if I wanted to get rid of surplus powder or use it in another caliber.
In my CZ527 Varmint .223R (1:9 Twist) I generally load 55gr Bergers for culling Roos but I also use 52 & 50gr. Then again I have also used 36gr Barnes VG which make a complete mess of a Roo's head at 200m, yet alone a Rabbit or Fox. No good for pelts or meat.
Enjoy your experiments, that's what it's all about.