You are right, there is a proportion issue with the rear of the Vulcan 900 Custom when no one is on it. It appears big K was going for a neo-Frisco chopper silhouette but got the proportions off by a tad and the rear fender is riding too high. If it had a 16" rear-wheel the proportions would be much better. Perhaps a simple accessory like slant-sided saddlebags would alter the visual height of the fender and close the gap between the top of the tire and the bottom line of the fender.
Alternatively, if the front wheel was a 19", the rear fender lowered, or lower and changed to a ducktail style but keeping the 15" rear-wheel, then youll almost have a big Honda VLX, which has a classic Frisco chopper silhouette.
Not to diss either bike, I commute on a VLX in the D.C. area 10 months out of a year rain or shine. And I have put the 900 Custom at the top of my consideration list for my next commuter. The price is right, the size is right (for my 29" inseam legs), the fuel injection is right, the power is almost right (wish it has at least five more ponies) and when some mid-size saddle-bags are thrown over the rear, the style will look almost right.
Gabe or fellow MOrons: Any info on the MPG? Maintenance? Other real-world riding info?