That's a nice looking blade, sucker rod will make a fairly tough blade, though I doubt it will harden up all that much...should be a bit better than RR spike though.
It will be tough to fit a handle that follows the back of the blade...
I've only done one hidden tang knife, and like Don said, you should center the tang in the with the blade...give or take a bit.
If you really want, you may be able to move the tang down slightly by laying the bottom of the tang on the anvil and top fullering at the transition area with the cross pein...
I've only tried this once, and I buggered up the knife I was working on, not trying to discourage you, just a heads-up...more experience people probably have better solutions.