Remember the old circumference formula- - - - C = Pi X diameter?

By dividing the difference in circumference (the gap change) by 3, you get the difference in diameter from top to bottom. The really anal-retentive types will go ahead and use Pi to as many decimal places as their calculator can handle. 3 is close enough for me for a guesstimate of cylinder taper.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!