mkirsch,
I use pressure treatded plywood or 5/4 treated deck wood cut to fit inside an angle iron welded frame for all the steps. The wood is covered with ouside runner black carpet stainles steel stapled on the bottom side of the tread and then wrapped around the wood tread ans stapled on the bottom side before dropping into and bolting in the step's frame. Hence, all the treated wood is covered and the finished step looks very professional. Welding where ever possible and grinding smooth is much stronger than bolting and there's no rusting of (unless SS or galv bolting is used) or tripping on the heads or nut ends of the exposed bolts. I like structural strength to be a big part of the finish project especially when safety of use/strength is in play. I refuse to cheap out or save a couple bucks on items/projects I do.
Maybe, I just think different but I demand to do it right the first time which means it basically won't require a second time and has a long lasting life. One of my porches, the rear step one (made 10-1/2 years ago) has well over 140,000 miles on it including trips to Alaska and most were with a 2000 lb plus trailer behind. The other, the side step one (made 6 years ago) now has over 90,000 miles of use and again, most with a trailer behind. The rear step porch is for our Lance campers that had a very close to center door and the side one is for the Lance's that have an off center door. Both work great for what they were made for and will as long as we use them or whoever after were done and gone as we're plenty old now but far from quitting!