My wife and I have used this yeast twice in variations of a Northern Brown Ale. The mash and fermentation profiles were nearly identical for these beers. We mashed at ~150-153 degrees for 60 minutes. We made a 0.75L starter on a stir plate for both. Both ales had a O.G. of 1.054 and reached a F.G. of 1.009 after 7 days. BeerSmith estimated a F.G. of 1.017 based on a 66.5% apparent attenuation but we got ~82% attenuation. At first we thought our mash tun profile was off in BeerSmith and our mash was more efficient, but even after adjusting parameters for a new mash tun we got, it repeated itself.
We're not complaining as this yeast makes an AMAZING English Brown Ale but I wonder if anyone might be able to pinpoint what would cause this yeast to attenuate so much higher then reported.