Cork might be better for the long term life of the star, but it would get torn up REALLY quickly. I have not had a problem with the wood and I'm still on my first set of stars. My cold steel stars seem to perform the best and are the most durable. I use 4.2 oz and 6.4 oz. The lighter the star, the harder it is to keep it flying straight at greater distances. I buy most of my stuff online from KnifeCenter(.com). Hope this helps.
Why not build a box frame with the top open so you can slide 4-5 1×6 boards in or out for when you need to replace a board also wouldn't have to worry about the knifes hitting screws