I cut a toile (mock-up) of the jacket in an inexpensive wool blend fabric I found at a local shop. It needed a bit of support so I interfaced the fronts with some leftover suit fuse that I had in stock.
Silvia put it together ready to fit. It's only a few hours to put a shell like this together- which I feel is time well spent when dealing with more difficult body shapes.
The front edges were just turned back, the collar was literally just a bias cut collar of the same fabric with the suit fuse for some stability. The sleeves were made up from a stock pattern that I already had in the approximate armhole size, but not basted in. Very thin shoulder pads were tacked in place.
The purpose for this was to just get a shape together to fit and make pattern adjustments. The clients hadn't even looked at fabrics, or thought much about the styling they were after except that it be single breasted and have a vent in the CB. I like to be able to pin on a pair of sleeves after I fit the body- just to give the client an idea of what it will look like- many people find it disconcerting to try to envision a final product without sleeves.
Obviously from the pinning you can see that I had to pin out at the shoulders(sloping).
I had a bit too much length through the front( as I suspected).
I needed to pin out a dart of about an inch of excess width at the front hem that terminated just below the chest. The back of the jacket seemed to sit well although I had to reduce the cross back width that I had allowed for. I will reshape the armhole all round.
The only other issue was his regarding his left shoulder. Due to a deteriorating shoulder, the ball of his shoulder was protruding in front and I will have to make allowances for that to be accommodated.
Next stage: pattern corrections from the fitting.