The flywheel weight issue is a bit if a red herring, I think. A slightly lighter flywheel will have less momentum and slow a bit quicker under heavy loads, but will also take longer to return to speed, too. But there will be no difference in power to do the job. A lighter flywheel is just easier to stop and start. The WC68 on my B2650 does a great job. I just slow the roller feed speed for bigger material.
Just remember if you get the WC68, the directions for shortening the supplied PTO shaft leaves very little room to fit the shaft onto the tractor and chipper when mounted on the 3 point. Cut it 1 inch or so shorter than specified in the directions. That leaves plenty of meat on the spline shaft to transfer power, and makes installing it way less of an problem than sticking with the instructions measurements - which do allow it to fit, but BARELY, and a major pain.
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