I would advise that you install a removable header tank.

Reasons.
Ease of repairs and adding  future modifications which often occur.  ie you desire to install electronic ignition. you can install the units under the header tank.  Access to firewall and a host of other ideas as well.  Yes, it takes more time to construct but the long term benefits outweigh the time factor.  You do enjoy building the plane. don't you?

Bob Smiley
N94RJ