I'm stuck in the traditionalist rutt so only use full lines. If I were to fish this rod I'd start with a standard Delta 6/7 multi-tip line, the old style Delta MT. I don't know the grain weight of the belly forward. I think there are charts out there in the internet atmosphere with the answer? I've never really fished a shooting head, have started a couple times but quickly, within 30 minutes, went back to the bank and changed spools.
My interest in these rods began with a Custom 13' 8/9-3, almost identical but rated for 8/9 spey lines. I used the Delta 8/9 MT on it but broke the tip section after 3 or 4 months. Sent the broken tip to Steve Godshall and he fixed it, sleeved it I presume. Still fish the rod but now with a Delta 7/8 MT. Love the rod so it makes sense to try to keep it going. The 7/8 with a spare tip gives you a little more lee-way to find a good line for it.
Thanks for the question J.James.