Eric,
Oops, I owe you an apology as I forgot the Aero clutch does not have the pressure plate like the big, ohv machines did. So my using the term pressure plate probably muddied the waters. I will strike that out in the previous reply.
The main thing, still, is to check that the bearing is not too tight. If without any springs installed the sprocket can be given a twirl with you fingers and it rotates freely and does not drag to a halt after a turn or two, then that sound fine. Once you start installing springs, I would expect the sprocket to start to offer resistance. Unless you pull the clutch lever, then it should again spin freely!
Referring to your illustration for item numbers: In normal operation, the clutch springs [2] press on the flange of the carrier/hub sleeve [13]. This applies pressure via the ball bearings [8] to the clutch plate [6] and forces it against the backing plate [12] to provide drive. The sprocket is along for the ride. Roller bearings [7] stabilize the sprocket and take the chain load. The bearings only come into play when the clutch plate is lifted, and allow the clutch disk and sprocket to rotate independently, and freely one hopes, from the flywheel.
When you operate the clutch lever, it uses the thrust ball race [5] to shove the whole sprocket and clutch assembly [6, 7, 8, 11, 13] sideways against the pressure of the clutch springs. Once the clutch disk is clear of the backing plate, it should be free. In the case of the Aero, there is no pressure plate occupying the void between the clutch disk and the inside face of the flywheel. This was used on the higher power machines to provide more capacity, the clutch disk had friction material on both side. So lacking the pressure plate, one does not have the problem of running out of space the lift the clutch disk. In theory if the lift were enough the back side of the clutch disk (the side not used for providing drive) could rub or drag on the inside of the flywheel. But I don't think one has enough clutch lever travel for that to ever be a problem. Also I would expect an metallic rubbing sound of aluminum on steel.
When you upgraded from 3/16 to 5mm rollers and enlarged the width of the grooves, how precise were the grooves cut?. Since the rollers do not have a cage, they rely on a nice fit in the grooves to keep them square to the race. It is not enough that they are crowded in there to keep them square.
As far as setting the clutch, you want the minimum amount of slack in the clutch cable so that you have maximum lift. I usually check it right where the clutch cable attaches to the clutch operation arm, behind the flywheel. So long as it can be wiggled in rotation just a smidgen, that is enough slack. Don't expect the thrust bearing [5] to ever stop spinning. It is enough to make sure the pressure is off it, having it idle along due to parasitic drag is unavoidable. Since the clearance is set to a minimum, you do have to check it often to make sure wear of the clutch disk has not allowed it to settle down on the thrust bearing and so bear the load; preventing the disk from bearing against the backing plate.
If the bearing balls [8] and their races are o.k., the flange on the carrier sleeve [13] should not come anywhere close to the clutch disk. It should never rub on it, or the grease slinger [11]. If the rivets for the clutch disk have been replaced by bolts or screws, you have to make sure they clear that flange as well.
-Doug