1.0
Measure the usable panel
The front of a cap is not a flat rectangle. Crown seams, buckram, embroidery zones, and curvature reduce the area where a molded patch can sit cleanly. Provide the usable width and height at the exact placement rather than the overall cap dimensions.
A paper printout at finished size is a simple early check. Place it on the hat, photograph it from the front and side, and include those images with the inquiry.