You should be able to replace the balls/retainers with nine 3/16" or 1/4" steel balls (check to see which is proper) without a problem. The dyno side cone gets threaded onto the axle and then the dyno armature is tightened up with the washer and dynohub side cone locknut. That gets put together real tight. Then, put the dyno side balls into the race in the shell, spaced evenly and well lubricated with appropriate grease. They will stay in position as you lower the axle/dynohub assy into the hub shell mating the cone nut with the balls. Hold it together so that the cone can't fall away from the balls and secure the axle on the dyno side into a vise or other method of holding the axle. Lube up the race on the non-dyno side and put the balls in place, insert the grease retainer (LB405) and screw the cone down onto the axle until it firmly contacts the balls. Then, adjust the cone for proper preload. This is a little tricky with a dyno hub as rotating the magnet around the armature causes magnetic, not friction resistance. Play with the tightening and loosening until you have just enough contact to eliminate any side play at the rim. Not too tight, just tight enough. Then hold the cone in position with a 16mm cone wrench (which you may have to grind to get a perfect fit as the flats may be slightly recessed into the hub shell) and tighten the cone with the lock nut (LB155). If you hold the axle tight and spin the wheel, it will rotate well. Trying to feel for proper cone tighteness at the axle doesn't work well because of the magnetism.