Sorry for answering, but FYI
it can also be outshined.
verb (past and past participle shone /SHōn/ or shined)http://oxforddictionaries.com/definition/american_english/shine?region=us&q=shine
v. shone (shn) or shined, shin·ing, shineshttp://www.thefreedictionary.com/shined
Although there is no entry in the dictionaries for outshine having as a past participle outshined, outshined is broadly used, esp. in American English.
But thanks a lot fredbär for reminding me of that!
Don't care about your being pingelig! I am very fastidious,too, which means that what I am saying, at least from a grammatical point of view, derives from a lot of research and experience in the study of the English Language.
But thanks anyway!
out·ˈshine <-shone [or -shined], -shone [or -shined]> http://el.pons.eu/dict/search/results/?q=outshine&l=deen&in=&lf=de