We had a little discussion about ballast weights recently vis a vis lanc mid upper turrets ,just post war (canberra a/c),the ballast weights fitted near the pilots seat (B2) resembled lead donuts and slid onto a bar,all largeish a/c have ballast weights fitted for c of g correction/adjustment.
On smaller (test and evaluation a/c) a/c I have seen specially shaped ballast weights bolted directly to fuselage frames.
Are any good cutaway illustrations available ? might be possible to identify the normal ballast weight positions from one of them.

rgds baz