Alaska Grades do not convert to NCSS Overall grades.
NCSS grades are not the same as Cdn Rockies Water Ice Commitment grades - generally speaking, to convert a WI commitment to an equivalent NCSS, subtract 1 to 2 numbers. For instance, Slipstream, VI 4+ as a water ice route, would be V WI4+ if rated as an Alpine route.
The whole system is confusing,and that's why Euro alpine grades make more sense.
Also, if you Do use NCSS its real important to use the Roman numerals. Otherwise, if you say Spindrift (eg.) is a "grade 5", do you mean its a
a) V, WI4
b) IV, WI5
or c) V, WI5????
d) you probably don't mean it's a IV, WI4.