SLI works in windowed mode. I can see both GPU loading with EVGA overlay, on my 480s. No need to guess or spread wrong information.
Here's the SLI profile for the 301.42 WHQL drivers:
Profile "Final Fantasy XIV"
ShowOn GeForce
ProfileType Application
Executable "ffxivgame.exe"
Setting ID_0x0095def9 = 0x00010000
Setting ID_0x1033cec1 = 0x00000003
Setting ID_0x1033dcd2 = 0x00000004
Setting ID_0x1095def8 = 0x02c00005
Setting ID_0x10ecdb82 = 0x00000001
Setting ID_0x701eb457 = 0x2241ab21 InternalSettingFlag=V0
SettingString ID_0x7049c7ec = "웭ꑢ쫐₰" InternalSettingFlag=V0
SettingString ID_0x704d456e = "쪣쀯㓵僽婙簭鹼瀮딕ᤠ及븄᱃뼍襢籜謬贷㱃矺糓ꗼ熟胆㖩뫬뛝쑖낡锛䭷乇솵᜶୭謸壺嫣Ͱ嚉誌㈡跽軧桧ⶇ䂚驐읒౦펴턖㛰눫" InternalSettingFlag=V0
SettingString ID_0x7051e5f5 = "籭鸙" InternalSettingFlag=V0
SettingString ID_0x705fafec = "웭ꑼ쫑₀쁰㒨傢婋籨鸹灰땁厈븞ᰒ뽉襂" InternalSettingFlag=V0
Setting ID_0x708db8c5 = 0x5c04c2a2 InternalSettingFlag=V0
Setting ID_0x709a1ddf = 0x4b1cd968 InternalSettingFlag=V0
SettingString ID_0x70b5603f = "榻鳈⏹ꢗ" InternalSettingFlag=V0
Setting ID_0x70edb381 = 0x24208b6c InternalSettingFlag=V0
EndProfile
Profile "Final Fantasy XIV Benchmark"
ShowOn GeForce
ProfileType Application
Executable "ffxivwinbenchmark.exe"
Setting ID_0x0095def9 = 0x00010000
Setting ID_0x1033cec1 = 0x00000003
Setting ID_0x1033dcd2 = 0x00000004
Setting ID_0x1095def8 = 0x02c00005
Setting ID_0x10ecdb82 = 0x00000001
Setting ID_0x701eb457 = 0x2241ab21 InternalSettingFlag=V0
SettingString ID_0x7049c7ec = "웯ꑢ쫐₰" InternalSettingFlag=V0
SettingString ID_0x704d456e = "쪲⃕쀳㓿僽娊籿鹫瀥딇ᤠ及빁ᰂ뼊褶籊謽⑅贽㰆矽粝ꖸ熉胙㖰뫡뛝ᯕ쑚납锐䭫乿솵ᢻ譪壻媦嚁ᚚ誊㈡跰軵桧䃴" InternalSettingFlag=V0
SettingString ID_0x7051e5f5 = "籯鸙" InternalSettingFlag=V0
SettingString ID_0x705fafec = "웭ꑼ쫑₀쁰㒢傢婉籮鸹灰땁厈븞ᰒ뽉襂" InternalSettingFlag=V0
Setting ID_0x708db8c5 = 0x5cf40380 InternalSettingFlag=V0
Setting ID_0x709a1ddf = 0x4b1cd968 InternalSettingFlag=V0
SettingString ID_0x70b5603f = "榻鳈⏹ꢗ" InternalSettingFlag=V0
Setting ID_0x70edb381 = 0x24208b6c InternalSettingFlag=V0
EndProfile
---------------------
Here's the profile for the beta 304.48 drivers:
Profile "Final Fantasy XIV"
ShowOn GeForce
ProfileType Application
Executable "ffxivgame.exe"
Setting ID_0x0095def9 = 0x00010000
Setting ID_0x1033cec1 = 0x00000003
Setting ID_0x1033dcd2 = 0x00000004
Setting ID_0x1095def8 = 0x02c00005
Setting ID_0x10ecdb82 = 0x00000001
Setting ID_0x701eb457 = 0x2241ab21 InternalSettingFlag=V0
SettingString ID_0x7049c7ec = "웭ꑢ쫐₰" InternalSettingFlag=V0
SettingString ID_0x704d456e = "쪣쀯㓵僽婙簭鹼瀮딕ᤠ及븄᱃뼍襢籜謬贷㱃矺糓ꗼ熟胆㖩뫬뛝쑖낡锛䭷乇솵᜶୭謸壺嫣Ͱ嚉誌㈡跽軧桧ⶇ䂚驐읒౦펴턖㛰눫" InternalSettingFlag=V0
SettingString ID_0x7051e5f5 = "籭鸙" InternalSettingFlag=V0
SettingString ID_0x705fafec = "웭ꑼ쫑₀쁰㒨傢婋籨鸹灰땁厈븞ᰒ뽉襂" InternalSettingFlag=V0
Setting ID_0x708db8c5 = 0x5c04c2a2 InternalSettingFlag=V0
Setting ID_0x709a1ddf = 0x4b1cd968 InternalSettingFlag=V0
SettingString ID_0x70b5603f = "榻鳈⏹ꢗ" InternalSettingFlag=V0
Setting ID_0x70edb381 = 0x24208b6c InternalSettingFlag=V0
EndProfile
Profile "Final Fantasy XIV Benchmark"
ShowOn GeForce
ProfileType Application
Executable "ffxivwinbenchmark.exe"
Setting ID_0x0095def9 = 0x00010002
Setting ID_0x1033cec1 = 0x00000003
Setting ID_0x1033dcd2 = 0x00000004
Setting ID_0x1095def8 = 0x02c08005
Setting ID_0x10ecdb82 = 0x00000001
Setting ID_0x701eb457 = 0x2241ab21 InternalSettingFlag=V0
SettingString ID_0x7049c7ec = "웯ꑢ쫐₰" InternalSettingFlag=V0
SettingString ID_0x704d456e = "쪲⃕쀳㓿僽娊籿鹫瀥딇ᤠ及빁ᰂ뼊褶籊謽⑅贽㰆矽粝ꖸ熉胙㖰뫡뛝ᯕ쑚납锐䭫乿솵ᢻ譪壻媦嚁ᚚ誊㈡跰軵桧䃴" InternalSettingFlag=V0
SettingString ID_0x7051e5f5 = "籯鸙" InternalSettingFlag=V0
SettingString ID_0x705fafec = "웭ꑼ쫑₀쁰㒢傢婉籮鸹灰땁厈븞ᰒ뽉襂" InternalSettingFlag=V0
Setting ID_0x708db8c5 = 0x5cf40380 InternalSettingFlag=V0
Setting ID_0x709a1ddf = 0x4b1cd968 InternalSettingFlag=V0
SettingString ID_0x70b5603f = "榻鳈⏹ꢗ" InternalSettingFlag=V0
Setting ID_0x70edb381 = 0x24208b6c InternalSettingFlag=V0
EndProfile