Worked on the Interim Cryogenic Propulsion Stage (ICPS) over the weekend (and earlier in this week), identical to the Delta IV build I did a while back with the exception of the top.
Those tabs are the bane of paper modeling. They should be cut off, and strips off paper glued to one section, fitted, then once aligned, glued. The paper tabs connected like that through the next piece off of the same plane of the parts, and it is virtually impossilgle to get a tight invisible seam.