tomaselli used to make different sized clubamns for large displacement japanese inline fours, which is why they tend to fit better. They also came in different drop sizes so it is possible to get a clubman bar that might be less uncomfortable than those ebay cheapies. The Tomaselli adjustable bars are probably the best if you are dead set on a clubman bar.
The ideal rider position is to have wrists straight, back straight and legs at a 90 degree bend to your torso. With clubmans without rearsets your back will arch concave, and the angle between your torso and legs is les than 90 degrees, not to mention that your hands and wirsts will be slightly bent (because your back is concave) and you are putting a lot of pressure on your bent wrists. low bars (clubmans and rearsets and sometimes drag bars) without rearsets will often lead to lower back problems, severe leg cramps, and wrist cramps, and it gets worse if your seat height is lowered too. A lot of this depends also on your height, a person who is 5'5" will not really have the same position problems as a person who is 6'5", and ther taller you are the more uncomfortable it will likely be. Lowering the seat can take a lot off your wrists but you can still suffer from leg cramp/ lower back pain.
of course the older you are the worse it feels sometimes...when I was 20 I could ride a cb750 with clubmans and no rearsets and think ok, this is slightly uncomfortable but I look damn cool. Now that I am 30 the same setup is not cool enough for me to ride it for more than 15 minutes. who knows how I will feel by the time I am 40.