screwing into slide-out walls?

Folks, we have the 178 with the kitchen that slides out.  I will be mounting a magnetic knife holder and a spice rack inside the area behind the sink and stove, wonderful things that my live-in gourmet chef says are essential.  I wonder if anyone has gauged the thickness of the walls and their suitability to accept a screw?  I have a couple of ways of mounting these things, but want to learn from others' experience whether screwing into the walls (carefully, of course) is a viable option.

thanks as always for helping me use already invented wheels!
Best, Jim

A 1 inch screw will be fine. Expanding moly bolts can be used, but they don't always work right with the foam core.

Marwayne, thanks, I had seen that picture before, and it is very useful. 

Are you confirming that the walls of the slide-out are the same construction as the main walls of the R-pod?  I have outside measurement of 68", inside of 65", maybe 65-1/5".  If the walls are 1-5/16" thick (times two), then I'm missing 3/8". 

I'm just being nitnoid. My measurements are likely off a bit.

Thanks, Jim

Excellent!  thanks much for the pictures!  
I'll verify mine isn't any different from yours (another shipyard thing -- not all ships of a class are built the same way) and quite probably screw into the same stringer for our knife holder!