An inside micrometer only takes a two point measurement. After a little practice and you begin to get a good feel for it, I would measure it, at least 4 different locations to check taper and roundness. Measure it about 1/2 inch down from the top, (write it down), then drop down about half way or more and do it again. Now rotate about 90 degrees and do it again. That is how I would do it. I would also measure over the tips of the inside mike, with a standard micrometer, as a way to verify your readings. If you do not read micrometers very often, it is very easy mis-read and be off by .025.
A dial bore gage is the way to go, that is if you have an accurate way to set it, like a master ring, or setting fixture. That would be the fastest, and more accurate reading.
But if you are patient, and have a good feel, you can get very accurate readings with an inside micrometer.
I have been using measuring instruments everyday on the job for over 25 years.
