Like Indian Larry said back in the day - a bike's gotta have at least one wire wheel or it just ain't right. Radial "laced" fatties don't count IMO. Honestly, the only real reason I dislike the stock NT rear is that damn "semi-polished" lip. It ALWAYS looks dirty if the bike has ANY true chrome on it also. With brushed and semi finishes, you've gotta go all or nothing or one just ends up looking misplaced.
(yeah yeah, get rid of the chrome stuff... but it's so shiny!)
Any ideas if an 18x5.5 fits under a stock fender? Everybody I've seen with an 18 either has a Heartland kit or some other non-OE rear fender.
It should just be a calculation. You have to use a lower profile tire with an 18... more thump from the road, too. Get the diameter of the stock and the 200-50... so 200-55/17 is 17 + (200*0.55)*2 or 220mm + 17" = 25.6" and 18 + (200*.5)*2 or 200mm + 18" = 25.87". The diameter is 1/4" larger. You can calculate the circumference difference if you want to see when you are speeding and your speedo says you aren't <grin>. If you are worried about the 1/4" stiffen your rear shocks slightly.
Since Harley Davidson wasn't worried AT ALL about the handling of a Nightrain when they put forward controls and a 200 tire on it, you won't care that the lower sidewall height also has a negative impact on your already poor cornering capability.
Yes my 02 Night Train carbrarated has a rear spoked wheel, myself don't really care for it rather have something little different,but hey that only my opinion brother..!!