I used to wear custom plastic orthotics during my child and teenage years. I think a really good substitute are Super Feet insoles. I use them in ALL of my footwear. And yes, you would need to remove the boots existing inner sole because if you don't, the foot/heel will be too high leading to all kinds of other issues.
As for the boots, thank you for the review William. I hope you will not get upset if I provide my own 2 cents?
I just purchased these a few days ago and they felt great in the store. So with the sale they were having, I bought them, not really needing them. I toiled back and forth about whether to keep them and was worried that they would not fit well. I heard about lengthy periods of break in and pain the first few miles from several different threads.
Despite my concerns, I decided to just try them outside due to the great return policy from the store. So far, the first 1.5 miles is great!!! Mind you that I also climbed 1,500 feet at the same time. The fit for my foot is amazing. I have used Danners in the past and while Danner replaced my High Grounds with new one due to warranty, I just never wore them again and plan to sell them brand new, never used. The first pair of Danners started coming apart at the toe after only 3 months of hiking. I guess I just didn't want to buy new Danners every year since they seem to fall apart so dang fast.
The fit of the Kenetrek us just amazing and the quality is second to none. I am not sure how I feel about the high heel compare to my Danners, but understand that they helped on steep sections, just made it more difficult on the rocky sections.
Overall, I am so impressed at how well these are made and how well they fit. I had a LOT of doubts about these boots but when I actually tried them, have no regrets.