Hey GB, I just about always stack cut three 1/4" pieces of plywood. I tried the FD New spiral blades and they just won't work very well at that thickness because they are not aggresive enough. If you will use the regular FD 2/0 spiral blade you will have better luck. I use the regular blades and they last about 30 minutes cutting that thick. I know some people on here say you are not suppose to stack cut that thick, but I do it all the time and it works for me.
Kim