Scatter shields are more of an RPM thing then a power thing. A lot of classes require a scatter shield. The truth is that the odds of a clutch coming through the floor on a 6500 rpm engine are extremely low. The biggest safety factor is running a good ignition based rev limiter. I had a friend I worked with at Advance who spent two months in traction because a clutch came through the floor on his modified circle track car. He was rear ended forcing his car up into the wall. The rear wheels came off the ground, with the accelerator buried. The multidisk clutch came through the floor and went through his right leg. His friend checked the memory on the tach, and the engine had gone over 20,000 rpms.
Now, there are two types of scatter shields. The most common type is a stamped steel replacement bellhousing. Keep in mind, this type of bellhousing is subject to bending, and has to be centered with a dial indicator. You can also get a scatter shield that mounts up in the tranny tunnel over the bellhousing. That style is more common in circle track cars. The clutch being SFI approved has nothing to do with a scatter shield.
I don't run a scatter shield in my car. I am satisfied with the risk, because it is a low rpm engine. Whether or not you want to run one is at your discretion. Honestly, on a 300rwhp low rpm engine, you are not likely to ever have a clutch come apart. Having a good MSD or comparable rpm limiter is much more important than a scatter shield.