Your A5 is not going to be very precise and only tell you one thing. Did it work or not? Are you going to say any load which works the A5 is automatically not usable in a double? If it worked, by how large an amount? If it did not by how much? And that assumes working an A5 has any correlation to being safe in a double.
You could use recoil calculations for a load as a better guide. Under 10 pounds ought to be safe, maybe 12 pounds. Velocity could be a general guide as well. 1100 fps on a one ounce load should be safe. But then you need to know pressures as well. There are one ounce load which generate higher pressures even with low velocity. A one ounce load, going 1200 fps that generates 11,000 + psi might be OK but I can find many better ones to load.
Give me known psi and velocity. I will pick a good one from there.
