Here we go!
In post #476 of the thread on xda, deltacity describes a very similar situation with flashing the e739 recovery on our c800 as you're facing right now: it didn't boot.
He noticed the stock c800 recovery was 8mb while the e739 was 4mb. I'm not sure what that could signify since our recovery partition ought to be larger than needed, not smaller (which obviously would be a barrier).
Why is it larger? Is there something contained in it that the c800 system requires??