1) The front drum (or clutch retainer) serves two purposes, it contains the clutch pack for 3rd/Reverse and the outer surface is where the kickdown band clamps the drum to stop it from turning in 2nd gear.

2) The sprag needs a load applied to it in order for the rollers to seat properly and serve as a clutch, when the tires are spinning in 1st gear there is a reduced load on the rollers so they don't properly seat; if the tires suddenly gain traction the shock can cause the rollers to "roll under" and fail....once the trans shifts to 2nd the sprag serves no function, it just rolls along like a roller bearing.

3) The sprag doesn't slow anything, it's supposed to stop the rotation of the rear planetary carrier which is necessary for 1st gear. The only time the rotating mass gets out of control is if the sprag/band fails to hold the carrier stationary....when this happens the cast steel front drum is driven at 180% of input shaft speed and can explode due to the centrifugal force generated by the overspeed.

4) Mopar fans love to talk about how "strong" the 727 is (it's called "brand loyalty") but it has weak points compared to some others...the sprag is only one of them.

5) Whether or not the sudden hook of the tires will cause sprag failure depends on a lot of factors including vehicle weight, horsepower and converter stall ratio. In many cases sprag failure is the result of cumulitive abuse, not a single incident. Repeated abuse can cause flat spots to wear on the individual rollers which will lead to failure down the road.

The bolt-in sprag only prevents the type of failure where the outer cam ring spins in the case, the most common failure is of the internal elements (springs/rollers). The pic below shows internal failure with the outer cam bolts clearly visible.

The best preventitive to sprag failure is a valve body with LBA and the use of manual low when spinning the tires or launching hard. A billet front drum is the best preventative to front drum explosion.