Wood is not a good thing to lay antenna elements on. Plastic is much better and even with plastic, you want to have minimum contact with the driven elements. And avoid having the washers intrude into the feedgap space, that in effect narrows the feedgap spacing.
Being located under 50 miles (LOS) from the transmission tower I'm aiming at really does not affect the antenna's performance. However, the next antenna I plan to build will utilize the build methods you recommend. Happy DX'ing.. . Bill