So glad you posted this. Funny enough, I had planned to take apart a licensed Gieves (by HF) and HF customized LP cashmere SC's -- both cheap and harvested for their buttons -- a la the Bodies exhibit, but never got around to it and ended up just pitching them. I'd planned to come at the canvasing from the front, though, rather than in through the lining. I was going to open one whole side and gently peel back all layers, one by one, and leave the other side intact, then set it up on my manikin. Again, though, other priorities intervened and I lost motivation.
I didn't have my mannequin when I did this. That's a cool idea. Going in from the front may be problematic though, due to the pockets and such. I should flip them inside-out and redo the photos though, and get a half-canvas in there. That's a ways back on the priorities list though, as you say.