I'm framing a tray ceiling in a new home we are building. Instead of a square tray, I'm going to build it as an elongated octagonal (Imagine a stop sign with two opposing sides stretched). I can think of several ways of doing it but I'm wondering if anyone has done this before and has any advice.

I currently have the larger bottom opening framed. My approach is to frame a continous rectangular ceiling above the opening and then use horizontal blocking between the joists to give myself a nailing surface to attach the angled 'rafters'.

So each 'rafter' if this is what they can be called will have two 45 degree cuts and look somewhat like a triagle. Each one will connect vertically to the framing on the lower ceiling and horizontally to the framing above. I imagine another way to do it is construct the upper ceiling framing so the rafters connect vertically to both the lower ceiling and the upper ceiling.

Maybe this is all a matter of taste but thought I'd through it out there in case someone has done this and can offer anything that I might have overlooked.