Thouroughly clean the inside of the cowl with 99% rubbing alcohol then scuff up the inside with steel wool or sandpaper to give some texture for the new latex to grab onto. If you're still looking to add structure if you paint a layer of latex then press pieces of paper towel into and and paint more latex over saturating it (kind of like laying fibreglass) it stiffens it up a lot after drying.
Can I ask how you used the pleather to texture the layer of plastidip? Was it as simple as pressing it onto the wet paint?