Master Cylinder - Push Rod Freeplay?

I've recently installed a new CB master cylinder on my IIA. Could someone give me more information on the process of getting the correct 1.5mm freeplay on the master cylinder piston via pushrod adjustment? I'm not really sure how this is measured, and I cannot detect by feel when the pushrod is actually making contact with the piston. I've gotten the pedal height adjusted correctly and would like to ensure this other adjustment is correct prior to buttoning everything back up and filling with fluid. Thanks!

We tend to do this from many years' experience and having "just a small amount" of play at the pedal is good...1/8"-3/16" should be fine.iu may find this easire if u open the driver's side door and look at the top of the pedal box with its cover off...that gives a more assurance that there is enough free play. That setting is not superfussy.

Thanks for your comment. This is something I haven't done before, so certainly haven't mastered the "by feel" method. I did ensure when setting the pedal height that the push rod was at rest and had no tension on it prior to locking it in place with the locknuts.