I have started work on a Viking hood in the style of the Skjold harbour hood find, also known as the Skjolderhamn Hood. I am basing my piece on the research presented in the Medieval Balticus blog, since I would rather just make something than spend time doing primary research right now. Besides that, her research seems pretty solid. The measurements she presents are in cm, so I converted those to inches, rounded up, and added a 1/2″ seam allowance on all sides. My Viking hood pattern is based on the measurements she gives in her pattern graphic, and in her illustration of the original garment.
The 9.5” slit is for the front opening of the hood. The 11.5” slit is for gore insertion under the chin. The 1.5” length of attached fabric above the gore slit is slightly larger than noted on the original garment, which was about 1/2” in length. The increased length is to allow for differnt heming styles on the hood opening, and to give it increased stability. If you want a smaller connected area, increase the length of the hood opening, NOT the gore slit. If you increase the length of the gore slit the gores will not fit smoothly into the slit and you will have to shorten your hem.
Most reconstructions I have seen show the body of the hood made with a long rectangle rather than a square. I think this is partly for simplicity, and partly because it is a more efficient use of wider modern material, reducing the needed yardage to 1/2 yard. The original square piecing would make more efficient use of a narrower hand-woven fabric, using most of, or the entire width. If you make your hood using a long rectangle (resulting in no seam along the top of the hood), be sure to join a short section of the hood in the front above the gore and below the opening for the face. I will mention this again later when I get to that point.