You should be able to see winglets with a new model file (as most SkySpirit 2012 767 paints have optional winglets). For example, if your .mdl file is OSX763ERV5_CF6-80C--AL.mdl, you can replace it with OSX763ERV5_CF6-80C--AWL. If you don't have a copy of the appropriate .mdl, you can download it from here:
http://ssp.cyber-ninja.jp/SSP2010Update.html.
Cheers!