"Lloyd E. Sponenburgh" lloydspinsidemindspring.com fired this volley in
. 3.70:

Be gentle when first starting the bolts in again so that you don't break
the "backer nuts" off the inside wall.

I could add that if you'll be removing/re-attaching the item any time in
the future, blowing some Great Stuff foam into the buck through the access
hole will help assure that the nut are still where you expect them to be
next time.

LLoyd