: I have no experience with what you are encountering, I purchased
: the full sized plans for my first project, but might I suggest
: perhaps photocopying the half on some clear acetate and then
: cutting out the edge so you can use it as a template? The clear
: acetate will make it easier to line up after you flip it.

Another simple solution:
Fold the paper prior to marking the template. Use the folded edge as the centerline. Mark the 1/2 form shape. Cut out the paper template. Unfold. One full size template.

StephenHJ