I should mention that the final finish I am after on the outside face is the textured matt surface that peel ply leaves. This means that sanding isn't an option. The inside face is glossy.

Obviously the full-size version was just my original idea prior to testing, so you most likely have a much better suggestion! It's hard to figure out the resin path when it's a 360 degrees pattern. The bit about the bag locking itself off makes perfect sense, we have the same issues when vac bagging wooden veneers and use breather fabric to ensure it doesn't happen. Getting the resin front to travel evenly across this shape seems tricky, especially considering the vacuum hose will have to be placed on the side face.