You can have him look at my crown tutorial... there is a chart for the different angles and what to cut the crown to joint them.
Alter Eagle Construction & Design
Where exactly is he having the problem? From the flat then up the wall to the higher crown at the vault?
You do install the crown at the vault ceiling as if it were flat, you have to keep the spring angle of the crown, if he has tilted the crown off of that angle then he'll have a time of it trying to match up the angles...
You keep the spring angle by using back-up like I show you in the tutorial.

He may have a good reason why he can't do it too... I'd hate to see him be second guessed by a guy on a forum 2000 miles away.

He'll need to make some sort of transition block or fitting which he can run the crown into from each side... the elegant options for this can be numerous and in fact will set off the moulding. Even a simple 1x block can be incorporated...

He currently has a 4x4 block as a transition with a very tiny angle cut into it to stick it to the wall. It looks weird. I know there has to be another way to do it. I'm going to go take photos of it today if anyone is interested in taking a look at the photos, email me.

By the way, I went to the Alter Eagle site and could not locate the information posted in the first reply.

Thanks!
Angela

It's linked all over, the front page, the menu, the list at the bottom of the page, from the forum, the owners tutorials, the drop down at the top of the page, and on & on... very easy to find.

I would think your carpenter may be best to assess this situation at any rate.

I've installed crown on numorus vaulted ceilings without any problem but it's always been a single room. Now I have the same problem as you. I've got a small hall extending off the room with a flat cieling. Did he find a solution?