We have had a 12'6" ULI inflatable for nearly one year now and love it. The board is stable stiff and glides very well . When given the chance to have a new 12'6" with the new Wiki rail we jumped at the chance.
There is a pronounced difference in stiffness with the Wiki board which has two skins and is a far bit heavier .
The new board glides much better and handles chop and boat wash as well as our Fanatic Carbon 14'.
On average we find the Wiki board about 1kph faster than the old board and under 1kph slower than the Fanatic Carbon 14' which really surprised us as we had thought the carbon board would be much quicker.
I believe the Wiki rail was designed to improve surfing performance but I can vouch that it improved flat water speed as well.
Never see much on inflatables on the forums so I thought I would share our findings
Cheers
John and Glenys