I don't remember how long the screws were. We just eyeball'd it. Maybe 1/2 inch? As my husband screwed them in, I watched on the other side of the wall to make sure it did not go through. There is some room inbetween the panels for the screws to go. If you use enough screws along the brackets, they will distribute the weight enough to no pull out when you place your shelves on them. We've had it for a yr. now and love it. This mod is def worth the effort for us. BTW-if you haven't opened your camper yet this year....go check...ALL our bed tents were holding water on the inside!!! Mattresses were ruined, panels were rippled, carpet wet. Thankfully it's still under warranty.
TV-2008 Ford Expedition XL
TT-2014 Shamrock 233S
Total Camping Trips...68 and counting!