I am a home baker and was trying to bake a R2-D2 cake for a nephew's birthday.  Covering the body part (not the dome head) was a nightmare!  The fondant was sagging and ripping.  I finally tried wrapping the cake and folding the top and bottom edges.  I also live in a high humidity area.  Any suggestions?

Hi,  I would personally wrap it and use the seams to my advantage.  I know I'm not much help here but that's how I would approach it especially because it's R2D2 (robot and all)  Can't wait to see your finished cake :)
 

when i did a R2D2 I put the fondant on in two panels with the seams under the arms/legs.  I have some in progress photos of the cake in my gallery photos, http://cakecentral.com/g/i/1861729/a/1862729/sort/display_order/