I used 1" of MDF for the top, but I think the supports were less than yours. I discovered the warp after laminating a paddle to it...

: Hi Bob,

: I've been lurking for quite some time as I built a cedar strip canoe, and
: picked up lots of great information here. Some one finally asked a
: question for which I can put in my 2 cents worth.

: I built my bench out of 1 inch thick MDF, and I really like it.the surface is
: smooth, I don't get slivers from it. and it is really flat. My bench is
: 8ft by 3ft, with supports every 2ft under the MDF.

: I was happy to find out the MDF is somewhat resistant to water. I keep plants
: on my bench, and have over watered at times, and not noticed for 1/2 an
: hour. only very minor (almost no) swelling occured. I'd give MDF the
: thumbs up for the bench top.

: Cutting it is pretty ugly though, you will be breathing a lot more glue than
: if you are cutting plywood.

: Well those are my thoughts.

: cheers,

: Myrl