I hope they make a standard stroke version too.
I have had quite a bit of exposure to the 612 long stroke models, and have participated in several 612 builds for iron barrel Fireballs. In most cases, it turned out to less preferred, and indeed, several users actually took the long stroke crank out and replaced it with a normal stroke HMC crank instead.
In any case, it presents a 22.5% increase in displacement. This creates a similar percentage of demand increase for intake breathing, or else the torque curve and peak rpm points will be commensurately reduced proportionally. In other words, the bike will run out of breath at a lower rpm unless something like porting is done to overcome the issue.
So, the added displacement boosts the torque curve, and makes it peak higher and earlier, which is good. But it runs out of breath earlier, which is not so good. It depends what you want.
An interesting observation is that they get 35 hp out of it, which is in a similar neighborhood as the rest of us are also getting. Why would that be? I'd wager that the 34mm intake tract is limiting the air intake at a certain amount in all our EFI engines, and that they are all running that 34mm OEM throttle body, and that's why we are seeing what we're seeing.
The 612 will see that 35 hp at a lower rpm than our Fireball 535, and the modded 500 at a higher rpm. All because the intake is thru a fixed 34mm orifice. Of course, there have been examples of up to 38 hp seen on dyno graphs here, but it comes down to the porting increases to help the flow do the best that it can at that 34mm MCSA, and also that the 500 demands a bit less air so it can rev a bit higher when breathing thru the same hole.
To get similar rpm range as a 500, the 612 will need a bigger throttle body and port. Without those things, the 612 will have a lower rpm limit, but with a fatter torque curve down below. We have also observed that the 612 doesn't seem to accelerate as fast up to speed, and it's just a slower revver.
Anyway, it might be just the right ticket for some riders, but not so much for others.
As for the piston, it looks nice quality, but the stock piston seems to be fine too.
I have ideas to bring the EFI up to greater heights, but I am afraid that the cost and the changes would not be in a category that the Enfield market would accept. For people who have the Ace head, there is plenty of upward capacity in that head to be ported for a larger throttle body or carb, and put out plenty more power and rpms.