To add more controversy over how good a measure KE is of a disks potential damage / safety issue etc.

The disk on Revolution 3 is a 12kg 8inch disk @2,500rpm and is very capable (done it) of flipping a 100kg robot clean over - easily.

If you calcualte its KE, it is not much more than that of Strip (about 7,500 KJ) - But in terms of damage potential / safety concerns, it is far greater (or so I would like to think).

Perhaps a simple table would work ie Disk Weight crossed with Disc Diameter and find Max permitted speed - This would still allow people more scope to optimise designs within the restraints.