I hear you there... The Nikasil plating in the aftermarket Harley jugs is sooo nice, but so is the cast iron liners used by Hammer Performance, they use a special blend that's rock hard to ensure a really long life with almost no wear, they even claim that they had to have some special diamond honing stones made just to hone these cylinders... Yes, I've been drooling all over their 1250 kit for my sportster and I got a killer set of heads set up and ready once I'm able to spend some more money on that bike, then it'll probably be faster than my fastest bike, the Intruder 1400 I got, that thing has enough torque to power wheelie just by cracking the throttle in 1st gear, no need to pop the clutch or pull back on the bars... that bike won't wait for you and will try to come out right from under ya... lol... Enough on that... I'd really like to see what a Sportster that weighs almost 200lb less with 110 hp and 90 ft/lb torque could do...
Now back to these engines... One thing I would really like to see is a good jug with a cast iron bore or an all cast iron jug with decent ports to use as a base for a killer build due to the durability and overheat forgiveness cast iron can offer, not to mention the ability to overbore in order to have better piston selection since there's a lot of 48 to 50mm pistons out there that would work really nice in these engines if we only had the right cylinder to bolt onto the bottom end.
So far, I've seen one with a Puch Athena jug with a 45mm bore and the crank stroked up to 45mm as well, and another with a Hebo Manston jug and they both ripped... I think the Hebo one may have been more powerful and faster, but the Athena was right up there with it. I have seen a few jugs on Treatland that have a cast iron bore that would probably work better than what we got now, but I don't think they could match the performance of the Athena or Hebo without extensive porting work.
Another really big concearn here is keeping the piston weight down in order to keep vibrations in check, a good static balance will help, but there's always that one resonant rpm that needs to be avoided since we only have one cylinder and balancing can only be done to make the engine run smoother in a certain rpm band since we can compensate a little for the off balance weight, but not so much for the piston acceleration using static balancing and balance factors to help modify what rpm band the engine will be the smoothest in. Heavier flywheels and solid mounting techniques can go pretty far for helping smooth out the engine, but with only one cylinder, there will never be a perfectly balanced engine that can run in any rpm smoothly... I'm still looking more into this and reading everything I can find to help me balance my next build. I do have to say tho that when I welded mounting tabs on my frame and solid mounted the engine it's the smoothest setup I've done so far.