Lets say my TopPos[0] was 0.5, TopPos[1] was 1.5 and TopPos[2] was 2.5.
And my CylPos[0] was 6.0, CylPos[1] was 10.0 and CylPos[2] was 14.0.
So:
[ TopPos[0]+CylPos[0], TopPos[1]+CylPos[1], TopPos[2]+CylPos[2] ] , is the triplet that expresses the location of the top centre wherever it is.
If you wanted to do something with these locations you could declare them as global variables and pass them to other objects to use as worldPositions or something.