Find the usable panel
Keep the label clear of shoulders, seams and moulded details unless the construction has been designed for them. On a tapered container, the outline may need to account for the change in diameter. A flat artwork view cannot show every fitting issue.
Make a paper mock-up at the proposed size and place it on the actual container. This simple check helps you judge the visual proportions and whether the label covers the intended area. Adhesive and durability still need testing with the proposed material.

