So, can you make the latest code available somewhere?
I'm trying to instantiate two fully unrolled instances of your "slightly older code" on the Cyclone V GX 7 target architecture - so far, unsuccessfully.
Once instance is placed and routed just fine, and achieves 140 MH/s in the conservative "slow" simulation and a whopping 250 MH/s in the optimistic "fast" simulation.
I still think the fastest you're going to get will be just a bit over the slow simulation based on my experience with the Cyclone II and Cyclone IV.
Dunno if you're interested, but if you'd like to get some idea for what's possible with Altera Hardcopy and you have modified the code to allow you to compile multiple instances of Makomk's code, you might try targeting a Stratix IV, EP4SGX530HH35 which is a prototype for the Hardcopy HC4GX25 ASIC (530K LEs). You could also try targeting one of the bigger Stratix V devices as a prototype for the Hardcopy V ASICs (up to 930K LEs) -- but I can't seem to find on the Altera website a list detailing which Stratix V is a prototype for which Hardcopy V like I can for the Hardcopy IV series. Don't bother trying unless you have at least 8GB RAM on the machine you're using as the bigger FPGAs really use up a lot of memory during compilations.
I'm guessing somewhere in the 2.4 GH/s range is possible with the Hardcopy IV, and considerably more with the Hardcopy V, although cooling the die may be challenging.
By my back-of-the-envelope calculations, it's going to take around $0.75 million in capital to launch such a project -- including the setup fees for the hardcopy ($200K), 500 ASICs ($500K), and a little more for the design and production of 500 basic mining boards. In order to beat BFL in terms of MH/$, it would almost certainly need to use the Hardcopy V ASIC which would conservatively give over 2 MH/$ performance if the ASIC could be adequately cooled. At today's difficulty/valuation levels, each one of those boards should be able to mine around 2 bitcoins per day, or $300/month, with a projected payback period of 5 months -- not bad. Any fearless investors out there?