: The strongback needs to be a little shorter than the distance
: between the forms.

: Why?

: Nick's book explains it well. The paper forms are mounted on
: material (usually 1/2" thick or thereabouts), and the bits
: of paper need to be facing outwards so that the strips can touch
: the edge of the paper.

: The end forms will be mounted on the ends of the strongback. So to
: get the bits of *paper* 17' apart, you need to allow for the
: thickness of the material you've used to mount the paper forms
: on. If your material you use for the forms is 1/2" thick,
: then your strongback needs to be 16'11" long.

On a more serious note, thanks everyone for your comments.... Since everything is already all cut out for an internal strongback, I'll build this one with the internal. Next time around, prolly use the internal as a base for an external since I do want to build more and the external is just more flexible that way.
BTW, I've assembled my strongback from 5/8 ply at 17', that way I can trim it down and get it just right :)

: Cheers, Ian