For an arrow pass, horn, bone, antler, mother of pearl or nothing at all.
You only really need an arrow pass if you are shooting heavy arrows with binding on the fletchings as these can rip into soft wood.
Someone will tell you that this isn't true, but I've had to put arrow passes onto Yew Warbows that have been severely worn so I know it to be true.
Good job with the bow, it's not easy to get 100# from a piece of Hazel
BTW, funny how subjective it is, I'd say right is still very slightly stiffer especially in the outer third. Over all much better and looking good, get some arrows through it and review it after a month's shooting to see if the tiller has shifted
Del