Galley hatch seals

I finished laying out a pattern for my sidewalls. I'm following the Steve Frederick manual approach for my sandwich panels. I have not located the notch for my hatch seal yet. Will I be safe in allowing a 3/8" space or should I go ahead and buy my seals first to be sure? I'm not really sure what to use. The seals on Grant's page look as good as any. I'm interested in what others have used for seals.