I was reading all of the replys here and thought that I would add my two cents worth

I take it one step further...... Many times my kit may have an abs cowl, if it does I use it as a mold and glass the inside after putting some furniture paste wax in it. It takes about an hour and I have a perfect cowl with very little if any sanding

Or sometimes I have glassed the outside of an abs cowl and made a perfect mold ... which I cut in half, attach wood strips to the edges, drill bolt holes, and then I can bolt it together perfectly lined up. I can pop out a new cowl in about an hour, over and over again!

If you had the need for a replacement cowl, post crash stuff, a mold like this could easily be made from you foam plug, before you pour the gas on it and erase all your efforts