A meeting place for rose breeders.
I'm glad you are going to work with that Ark-op :0). I haven't had the opportunity to use it very much yet, but from my limited experience it is a little challenging to get seeds from either way and is a little better dad. I think it is a little finicky for the right combination that would take, just like R. arkansana, but with the right mom hopefully there'll be good fertility.
It may be location, but the only seeds I ever got from David's Ark OP were from the pollen of another arkansana hybrid. It stubbornly refused pollen from everything else I tried on it, and I finally lost it a year or two ago. The pollen parent was a cross of Carefree Beauty and an arkansana clone that I got from Larry Davis. If David's Ark OP seedling did have one of his CB seedlings as its pollen parent, that may help explain the compatibility. I still have two seedlings from that cross which haven't bloomed. One went into the ground this winter, while the other is still potted. The only successful cross I can recall offhand using David's seedling as the pollen parent was from its pollen on Cal Poly. I shared OP seeds from my Cal Poly X arkansana hybrid seedling with a few of you in years past, but I no longer have that seedling, just a few descendants from it.