Confirmed this.Also double check that your lens doesn't have a lever to open it up for focusing and if it was open rather than stopped down.
The interesting thing is I have a pile of salvaged paper of unknown origin. The old Luminos paper was about 1 f/stop faster than the old ILFORD post card stock. With the ILFORD post card stock I was able to get into 6 seconds at f/11. I have some fresh ILFORD 5x7 coming so I'll have some known good paper stock to work with soon.For a 5x7 from 35mm, I'm fairly sure I use f16 to get times I can use and that still just gets me around 8-10 seconds. I know the old rule about always stopping down two stops from fully open, but I consider that to be bordering on BS, depending on the lens (I have Componon S lenses and they certainly don't suck). If you shouldn't ever ever ever use the other apertures, they wouldn't be there.