From the
local rules for the pre-Worlds and copied most likely from results of the
2014 CIVL Plenary (minutes yet unpublished):

Prototypes are allowed in test competitions (Cat. 2), but not in
the World Meet (Cat 1). The new prototype control rules have been adopted and
will be in effect for the World Meet in 2015.

Prototypes are gliders that are outside the manufacturer’s tolerances of
specifications or construction plans as published.

Measurement tolerances will be those provided by the manufacturer or .05%
(.0005 times the length). Battens must be as true to the glider’s published
pattern as possible.

Seems like paraglider pilots had something to do with this. "As
true as possible..."

The span of a Wills Wing T2C 144 is speced (
http://willswing.com/prod2.asp?theClass=hg&theModel=T2 ) at 32.3 feet 
approximately 32 feet 3 19/32 inches (0.05% of this span is approximately 3/16th
of an inch).

I measured the half span from the tip of the wing (without wing tips) to the
center of the back end of the keel (where the keel and the stinger come
together) and found the length to be 15' 11.5" when the VG is off and 16' 2"
with full VG (to the stopper). I have no idea whether I should be measuring to
this point on the keel to get half the span. It "seemed" about right and it was
a definite repeatable point.

Here is how you can make this measurement according to CIVL:

Check the glider’s overall span at full VG by measuring from the
extreme tip point to extreme tip. This measurement may be made easier by
measuring from tip to a point on the sail in the center on both sides.

I have no idea what the error bar is for my measurements as there
are numerous factors which would increase the width of that bar. As the VG
setting is not specified in the CIVL prototype rules, it is unclear how a person
doing the measuring can strictly apply the rules as they were obviously created
to require.

Check the glider’s wing profile by comparing the battens to a
pattern or another glider’s battens.

I look forward to see how this works out in Mexico next year.