I have a leigh RTJ400 and will use it to cut 3/8" box joints. They provide a straight bit but recommend using a spiral bit. I don't have a 3/8" spiral bit, but I do have a 1/4" spiral bit. Would it be a good idea to run a 1/4" bit through first and then the 3/8" straight bit. It seems to me that hogging the wood out first will allow the straight bit to do a better job... but what do I know.