Thanks Slowjohn, i get what you are saying about having it polished smooth so that the plug stands a chance of pulling out and that's what i'll try and do, so i can just you automotive wax as a release agent? I suppose any wax residue left on the inside of the cowl can be cleaned of so more glassing can be done on the inside? I don't care too much if the exterior of the cowls aren't perfect because i'll wet sand any bumps out.
The plug is the exact length i want the cowls, is that OK.
I'd need to know how much extra did you allow yourself on the open end?
I'm not sure what you meant by this.