I found frost to be the most boxing friendly. Check out this post:

http://www.dual-boxing.com/forums/index.php?page=Thread&threadID=17572

Note that in my macros I've made some changes. My trinkets were moved to the water elemental/mirror image button. This is because A) Water elemental and mirror images both benefit from increases to spell power. B) With proper glyphs and talents water elemental works well with a 2 minute recharge trinket.

I've benched my mages for the time being to level up my 2nd set of boxes, but you can take a look at their specs on the armory to get an idea of the stuff a boxer might take.