This being my third Benroy/PMF build I thought I would record the actual shrinkage I experienced using Big Duck 10oz cotton canvas and TBII (50:50 dilution) on rigid foam (XPS). The original reference lines were very close to the spot where I dry fit the canvas. I don't pre-wash, pre-shrink or iron the canvas as the shrinkage that does occur pulls out folds and other wrinkles when applied. This application proved to be very minimal shrinking. YMMV. The canvas was applied on a humid, rainy day with temps in the 70s. I think the difference in the port and starboard sides is due to gluing the starboard side first which pulled the port side canvas a bit before applying the glue to that side.
I hope this info helps anyone that is contemplating PMF and wondering about shrinkage. I used 60" wide canvas on a 49.5" wide body and had close to three inches of trim on each side after the overlap of the wall canvas. Lengthwise I had about six inches of overhang front and back (after tucking the canvas under the floor in front about four inches).
At the roof/hatch hinge location - 5/8"
Front roof/wall corners - 3/8" and 1/8"
