Have inserted Birkenstock inner soles because just wasn't getting the sort of heel protection I needed.
Due to an injury on the heel I really needed better protection than the boost offered. Anyway I have been getting the occasional sharp pain through the heel of the shoe on lunge steps. No doubt it is my own fault footwork however with an injury (Achilles Bursitis said the doc) I needed to act.
The Birkenstock Birko-contact insole are just a 3mm soft compound inner sole, with high arch support, but on the bottom is a much harder plastic compound that is 8mm thick that cups the heel and extends underneath past the arch to just behind the metatarsals.
https://www.birkenstock.com.au/prod...eel-cup-in-birko-flex-blue-footbed-insole-581
The softer insole glued on top the harder under-sole is an effective combination.
My first hitting after recovery have given no shocks.
OVerall, by way of comparison, I do think Barracades give better heel protection (wider, firmer), but the Boost is so responsive and nice underfoot that it gives a different sort of energy return but perhaps at the cost of as-effective heel protection.