I just finished my bed its 7 boards. The widest was 7.25 inches. I suspect the reason people use more boards is availability of wide lumber. It costs more than narrower strips. The advantage of narrower strips is that they will likely cup less. It requires additional bed strips and bolts however. I bought a complete stainless set from Chev's of the 40's but they bought it from Mar-K. It included the strip bolts and the bed to frame bolts. All great quality.