Thanks to all for your input.

After thinking things over in greater detail I've come to the conclusion that my sand bag idea is a bad one. Any object not secured into a fixed position within the airframe would surely slide rearward under acceleration and forward on deceleration. Not good.

I did experiment by placing exactly 2 ounces (57 grams) of loose clay powder within the nose cone and noting the shift in overall center of mass when the clay was all the way forward versus all the way aft. The nose cone is approximately 14" in length, tip to base, and the shift in CM was about 1/4" in favor of the forward weight. (I did place a spent AT G80 motor containing sand fill to represent liftoff weight in the motor mount.)

It looks like this bird will need about 3 ounces of something in or on the nosecone to acheive one caliber CM/CP, and it won't be in a bag.

Maybe I should stick to my political posts?