Ed, I cut my arrows at 30" for my 56#@26". They would probably shoot from heavier bows plus if you cut them to 28" they should handle 65# easily and maybe more. My arrows are around 600gr=/-. These cane arrows are about 3/8" at the point end and about 5/16" for the nock on a 30"arrow.
I actually prefer sourwood over the hill cane and also like red osier but have only made a few dogwood arrows. We have silky dogwood here, also a red stemmed dogwood but I don't think they are as good as red osier. I'll cut some some this fall to try.
Here in the NC mountains where hill cane grows is in the 6 to 7 hardiness zones. Even though the cane is deciduous the rhizomes run right under the surface of the ground and our ground rarely freezes more than a few inches.