Major update...
So I did some research on Grilamid plastic and how easily it can be formed and if it will actually retain the changes. Turns out that you need to be careful, but it's not too terribly hard to work with Grilamid. After realizing that I needed more forward lean on the Fischer Ranger 130 shells, but not via just tipping the whole boot forward more (via a thicker heel shim), I decided to give heating the shells a shot to add more forward lean to the shells.
I heated the shells at 175* F for ten minutes. This is well below the recommended temps I found, but I wanted to start out more conservatively and I didn't want the heat from the shell to modify the thermoflex liner. After heating, the shell was super pliable. I had previously checked my fore/aft stance position in another pair of my good boots to get some reference points on how to stand. I used a piece of furniture to press my knees against in order to reliably reproduce the correct position. With the heated Fischer boots on, I re-assumed that position and allowed the shells to cool for 20 minutes (until they were cool to the touch). The position is also holding the correct stance width and I placed a 3mm shim below the heels to negate the GripWalk "hump" (as
@pliny the elder advised).
Once the shells cooled I removed them and let them "settle". To my surprise, I actually nailed the changes I needed on the first try and the shells are retaining the increased forward lean. The forward lean is now at 16*. Some additional benefits of the heating are that the instep height has been lowered and the lateral cuff alignment improved. I needed both of these things, but these are "side effects" that you should be aware of when a boot is heated, flexed forward and allowed to cool in that position. Had I known it was going to be this easy, I wouldn't have even built the heel shims. I've never had luck with PU plastic boots when trying to increase forward lean by heating the shell, so I'm glad that Grilamid is easier for re-forming.
I'm really looking forward to skiing these boots again, now that I think I have the alignment issues resolved.