Side wall construction of my octane 222

[rcmike]

I'm wanting to put a stainless steel folding removable shelf on the outside of my 222, can someone enlighten me on what size the wood studs are if they are wood and how far part should they be from jayco building the trailer if someone has had the experience in this area . I'm thinking of taking the inside wall one section apart to see but that might be time consuming but I would know for sure. I can push on outside and all to see but I sure would hate to drill a pilot hole and it miss something solid It looked like when I go to other side where frig,water heater equipment that its not 2x4,,it's like 1x3 studs. Is there any uniformity in the frame on other side does anyone know ? Thanks