: Use 3/4 inch plywood.

I had thought of that but plywood in general is not readily available. (at least where I have looked) Not to mention the cost. I priced an 8' by 4' length of 9mm ply at 31 pounds. Thats about $52 US. So I'm looking for something a little less expensive. I should have mentioned that in my previous post. Thanks for the idea Judson. I again read that post and there you have it. At the time I was considering the strongback but was mainly concerned with cutting the forms.

Ed, I'm going with the MDF for the boxbeam in 3/4. The 1/2 inch space within the boxbeam will give me an easier way to get it to length.

Thanks for your assistance. As always great advice.

Cheers
Jeff