There's a violent explosion and a cleanup crew is sent in to collect the pieces of your feet.
No seriously, I'd think about finding a traditional wide boot, plenty of good ones in the 102-104 range out there these days, and stretch the h*ll out of it. I'd think twice about customizable models with several kinds of plastic because as far as I understand it, the plastic in the "customizable" area is thinner and more pliant to begin with. So taking it beyond its design parameters seems to be asking for structural weakening.
I'd also disagree with the comment above about grinding. Which can remove a mm or 2 of plastic for refining an already decent fit, but if you plan to really go mining, unless it's a plug, you end up with regions so thin you can push them in and out with your thumb. Happened to me, y'see.
And removing liner is a recipe for getting gradual buildup of pain in areas where the shell presses or bangs against the bones of the foot. IME, also been there too.