Wilderness Systems Sunshield - for Aspire, Pungo

Spray skirts are primarily designed to keep the inside of your kayak dry. They have a waist tunnel that create a seal around your torso along with a full deck that covers the entire cockpit to prevent most or all of the water from entering your kayak. The Sunshield provides coverage over the front portion of the cockpit and is a great option for blocking small amounts of spray, drips, wind and UV rays during light to moderate paddling conditions. It also allows you to enter and exit your kayak freely without the restrictions of a spray skirt. It is not designed to prevent large amounts of water from entering your kayak in heavy to extreme conditions or in the event of capsizing.

The Sunshield is fairly universal and works great for cockpits 45 inches and longer. On cockpits shorter than 45 inches, the material begins to overlap the seating area and may need to be pushed forward to create more room, however, that causes it to bunch which makes it less effective during harsher water conditions.

Should fit your kayak if you get W12 size if it doesn't quite fit my bad because I do not own a pelican mustang 100x but if you can fit it on your kayak it works really good and block out some waves too

Yes. The Sunshield will fit on the cockpit of the Pamlico 13.5.