Wyman Resistance Method Verification

I am trying to validate my Wyman power and resistance results from MAXSURF Resistance, however when following the very little information available from MAXSURF on the equations used for this analysis, I always get a lower HP value than MAXSURF predicts. 

My question is, following the equations described on pg. 14 of this website: http://www.westlawn.edu/news/WestlawnMasthead06_June08.pdf, can I verify the power results using the SHP in that formula vs. the Wyman HP output in MAXSURF Resistance? 

The equations used in the above website are: 

SHP=(displacement/1000)*(speed(kts)/(Cw*(LWL^(1/2)))^3

Cw=(0.8+0.17*(SL))

SL=speed(kts)/(LWL^(1/2))

Where if I pick a speed to verify, using the LWL and displacement, I have been unable to match the HP calculated in MAXSURF Resistance. 

I figure I am either misunderstanding the Wyman equations, or MAXSURF is including something I am not!