Part 4: Cutting the robe fabric
The vertical lines of the pattern are on the straight of grain.
Let's start by making a proper-sized pattern out of the diagrams. The principle is explained here. Lengthen front and back parts from the treble darts down depending on your height and the size of your panier. The back must also be extended horizonatally: Add 70-80 cm starting from the point marked "53", resulting in a back part of about 135 cm width. Remember that if you're very tall, you should add even more. At a height of 185 cm, a 150 cm wide back part will be just about enough.
Determining the back length is relatively simple: Use your overall height. This will result in a small train as every sack dress should have. Having a longer train certainly doesn't hurt. The taller you are, the more you should add to keep proportions. E.g. if you're 160 cm tall, use 160 cm. If you're 170, make it 180. If you're 180, make it 200. That's just a rough estimate, though. I have not much experience with gowns for tall people, so err on the generous side if your budget allows it. Cut the bottom edge straight.
For the front, measure from the waist sideways over the panier. That's how long the front must be from the waist down. (This is only true for pocket hoops.) Add 10 cm just to be sure. Also compare the dimensions of the sleeve pattern to your own measurements.
If you have a fabric that is wider than the 135 cm required for the back, be generous: Unless you're into patchwork, you won't be able to make anything sensible of the 15 cm strip left at the sides, so simply add that part to the back, part to the skirt portion of the pattern. Same goes for the front. You can harldy have too much fabric width.
If your fabric is only 90 cm wide, it's not much of a problem, either: Above, we had two halves of 135 cm each, making for 270 cm overall back width. That's 3 times 90. So cut two lengths according to the pattern as far as the fabric goes and a rectangle as long as the other two.
Cut each piece twice. Leave a lot of allowance at the top edges of the front (~10-15 cm) and the skirt (~ 5 cm). Depending on the shape of your shoulders, you'll need all of the allowance on the front part or none, but in most cases I've seen 10 cm were barely enough.
As an experienced seamstress you'll know how to economically puzzle the pattern onto the fabric. Just a few hints: Begin with the largest (i.e. back) parts and work down to the smallest. If your fabric doesn't have a pattern, try placing the front parts top to top so that their narrower upper portions lie side by side. After cutting the dress back and front and before cutting the smaller parts, measure the amount needed for the petticoat from the other end and mark it off. If there's still enough left for the remaining parts, go ahead. Otherwise you may have to make the "cheat petticoat" (see part 1) after all.
Next step: Draping the robe