Hello, thanks: no rust at all on either the bolts or the t-nuts. I did replace t-nuts at the same time as the bolts. Yes, these are the two bolts that hold the mono-extension down with the cradle under the extension. I used a torque wrench to check the torque on the bolts and they were spot on at 5 Nm. EDIT: this should read "7Nm".
Thanks!
Nicole