One of the advantages of the after market Booster Straps for ski boots is the ability to custom place them. Ideally, this is where they can actually cinch the top of the boot liner as opposed to just the hard plastic shell above the top buckle which is not as effective.
If you have high end ski boots with a decent power strap, you can actually easily modify it to be more effective without completely replacing it.
- Remove the power strap
- Drill new matching holes as close to the top of the rear cuff as possible
- Remount the strap in the higher holes
Now the strap is in a location where it can actually cinch the front of the upper liner snuggly around your lower leg: 
