How can I create false beams or plant-ons on a sloped ceiling?

[Arkytek]

I have created a vaulted ceiling in a kitchen/family room, with plank surface on that ceiling.  I would like to add some false beams (plant-ons) that follow the slope, to simulate using 4x10 T-1-11 panels with the joints hidden by the plant-on false beams.  I read how to do this more or less with soffits that follow the slope of the ceiling.  I even managed to create two that meet each other at the peak, without shooting out through the roof.  At least I think so.

 

What I cannot seem to figure out is how to precisely control their placement along the ceiling so they will be precisely 10' from each end of the ceiling of this 30' long room.  I want to create two pairs like the ones I have shown here but thought I should learn first how to place them along the length of the room's ceiling.

 

 

[Rookie65]

Once you have the 1st set where you want them, try using the transform/replicate tool in plan view to move them along the ceiling at the desired spacing.

[Arkytek]

I did that, Keith, sort of, but have yet to figure out how to precisely control the spacing/positioning.  The attempt at ad hoc placement did however make me realize that, if I'm going to have such plant-on beams for real, I'll need to size and space the placement of the two dormers accordingly.

[Arkytek]

I just opened my file today, to grab this picture better showing the dormer windows, and discovered the solution or at least think so.  I now see that the "beams" show up in plan view and can be rearranged there.  Will work on this later today and report back. Have to actually build things today so can't work on until later.

[Arkytek]

Waiting for helper so was able to come back to this.  Even managed the half-beams at the ends.