I was previously running my booster strap under the plastic tongue on my Kryptons (to eliminate shin bang) He recommended the Booster on the outside.
After adding the material, the boot is snugger, but after an hour or two I was getting severe pain, only on my left foot. Pins and needles type of pain. The only way to relieve it was to remove the boot for a couple of minutes. Then all good...for a while.
Two additional factors: I am prone to having my legs swell (due to medication). Not sure if the altitude made that worse. If so, weird that only one foot was bothered.
Also, he did some modifications to my footbeds. While he did add material (at the heel) much more was added to the right foot, which had no problems.
I'm not sure if it is the added material at the shin or under the footbed. There really wasn't much added under the footbed.