I was however watching these superb videos by Nick Birmingham:
which has made me reconsider this design or a design based on it. The bags themselves very much do not appear to have been worn in the style we might think of as a quiver and do not match illustrations of Gaelic archers at all. Indeed looking at Nick drawing the arrows it seems that these bags would (if worn) suit arrows being drawn from the bag point first, again inconsistent with the artistic evidence.
It seems that in English archery and Gaelic archer have the opposite problems. The English have good evidence of bag construction from extant examples but little evidence for how they were used, while in Gaelic archery the opposite appears to be true.
A spacer would seem necessary to prevent arrow heads" fouling on each other "bow and arrows barbed with iron" though were not used by all cultures so maybe not. It does seem that a more simple arrow tube made of leather that leaves the fletches free would be more apt. Choices for leather include cowhide, sheep goat and deer. With cow and deer being thicker and more tear resistant. Though I promised myself I wouldn't use a hair on barbarian hide I do have ready access to hair on hides and think a summer roe would look wonderful!
Hmmmm time for a think!