I currently have a 2012 R5 VWD LTD w/Dura Ace 7900 and Dura Ace compact cranks. Can anyone tell me if this can be done. I have read a few things saying it can't but none of them were on a 2012 model or an R5. Thanks for the help.

why couldnt it?
are you trying to put the wires inside the frame? that may be a deal-breaker on the R5, without mods that would void the warranty.
best options are to either leave the wires external or send the frame to calfee for their internal battery/internal wiring frame modification.

Not sure if it would be the case with the R5, but on R3's the front derailleur hanger needed to be trimmed at the bottom which leaves very little 'flesh' in that area. The hanger on the R3 is aluminium and can be replaced if it breaks. The R5's is carbon and moulded on, so if something goes wrong after trimming it down......

But still, if you can make it work, you're still left with cable stops sitting on the frame like pimples

I know it is a different animal, but why not go for an S5, it has all the facilities to accommodate Di2

Because I already have the R5 VWD. I originally ordered an S5 but after 3+ months of waiting I decided to go with the new R5.

Did you complete your Di2 build on the 2012 R5? Ihave had my R5 for a couple weeks...beautiful bike. Just bought an Ultegra Di2 upgrade kit and was wondering how the front derailleur issue was resolved. Did you have to shave it down for the compact crank? I have a Sram S950 and hoping everything fits! Any insight on your build I'd love to hear it!

I ran DA Di2 with a 2012 R5 VWD before I sold the frame. I didn't have to trim anything but I don't know if the clearance is the same as the Ui2. I was even running a compact crankset and it fit like a glove. If I needed to lower the derailleur more, I probably would have needed to trim it.