Try drawing out your concept. Lay out the lengths and diameters, and any important details such as the actual "bevel" angle of the end caps. Do this carefully, and
do it to scale. Then you can pick off target diameters at a number of points along the length of the blank, and refer to these as you turn the blank. Always stay to the safe (underturned) side of the plans as you work toward the final shape and dimensions. This is a simple method to arrive at a desired profile, instead of just going at it, hopeful
that you end up with the envisioned profile.
Maybe we will see something "new" out of your efforts.
Happy turning!