Hi Francis,

The debate on this will go on forever, but I can tell you what worked for me !!!

I used MDF to build a 4 x 2 strongback. I only had 4 foot lengths and I staggered the joints. I supported it using three trestles arranged longwise so I had six support-points. It worked perfectly ( I think three trestles was a bit of overkill, I could have used two ). The only thing I regret was making the cutouts in the forms oversize ( to allow for adjustment ). In hindsight, I think I would have had an easier time making the cutouts a tight fit on the strongback as the alignment would have been so much easier.

I used MDF for the forms also, with wallpaper paste to attach the drawings. I had no problems with this.

The only recommendation I have if you use MDF is to use a good quality respirator as the very fine dust produced when cutting gets through/around those cheaper moulded face-masks.

Anyway, good luck with the building.