Just Let It Flip? How Do I Sing through the Passagio During Open Vowel Exercises?

When I'm working through an open vowel exercise, and my voice wants to flip hard from chest to HV (and vice versa), should I just ignore it, until it hopefully smooths out?  I've tried getting really soft right at the transition point in order to make the transition smoother/less noticeable, but it leads to strain.  I've also tried just injecting a consonant (like 'n') right at the break point, but want to know if there's a better technique.

Great ideas! I'd consider using a narrower vowel (like OO or EE), since those tend to ease the transition into head voice. Your instinct to reduce volume is also spot on. Another thing to try is doing the same pattern on something semi-closed (like an NG sound). 

Over time, register-crossing exercises, slides, and mix-building exercises help to smooth that transition. See below for a few lessons I think will help:

https://www.30daysinger.com/tutorial/developing-each-vocal-register/1

https://www.30daysinger.com/tutorial/mixed-voice-101/1

https://www.youtube.com/watch?v=JDj-DBj7G4Q

Thank you for responding! Your tutorials, and youtube video were all very helpful, and took the mystery out of this confusing (at least for me) topic.

My pleasure! So glad to hear that.