Using the CHE code (with DSSV and MRST2002) I compared W+ and W- AL for center of mass energy of 500 GeV (blue) and 510 GeV (red). The change is small as expected, with a difference at mid-rapidity of less than 2%.
For completeness here are the numbers.
W+ pp500 eta=-2.25 AL=-0.133037 eta=-1.75 AL=-0.182091 eta=-1.25 AL=-0.232155 eta=-0.75 AL=-0.279067 eta=-0.25 AL=-0.319352 eta=0.25 AL=-0.372557 eta=0.75 AL=-0.414688 eta=1.25 AL=-0.451781 eta=1.75 AL=-0.514307 eta=2.25 AL=-0.673576 W+ pp510 eta=-2.25 AL=-0.120075 eta=-1.75 AL=-0.174056 eta=-1.25 AL=-0.228382 eta=-0.75 AL=-0.274046 eta=-0.25 AL=-0.319099 eta=0.25 AL=-0.372434 eta=0.75 AL=-0.415329 eta=1.25 AL=-0.456592 eta=1.75 AL=-0.512755 eta=2.25 AL=-0.669555
W- pp500 eta=-2.25 AL=0.018842 eta=-1.75 AL=0.0109192 eta=-1.25 AL=-0.00172645 eta=-0.75 AL=-0.00303291 eta=-0.25 AL=0.0446768 eta=0.25 AL=0.162059 eta=0.75 AL=0.287828 eta=1.25 AL=0.388246 eta=1.75 AL=0.448878 eta=2.25 AL=0.503238 W- pp510 eta=-2.25 AL=0.0195878 eta=-1.75 AL=0.0122011 eta=-1.25 AL=-0.000138017 eta=-0.75 AL=-0.00157857 eta=-0.25 AL=0.0450428 eta=0.25 AL=0.161664 eta=0.75 AL=0.282632 eta=1.25 AL=0.381473 eta=1.75 AL=0.448442 eta=2.25 AL=0.504252