A little more information...
The details:
I went slow with the dremel, only using as much speed as was necessary for the cutting tool to work.
A fine sanding drum worked great on the plastic. The two pieces of the clamshell were held together in a padded vice as I trimmed at the front. Keeping the axis of rotation of the cutting tool parallel to the centerline of the chassis gave the cleanest cuts. I had to trim the ridges inside the top, as well as the outer housing.
A carbide cutting/milling bit worked best on the aluminum blast tube.
I would trim just a little, then re-fit, repeating as necessary so as to remove the least amount of material necessary.
It took several hours of work spread over 3 days to get it right to my satisfaction. Patience was critical to getting a good result, as well as knowing when to set the tools down and walk away for a while.
"Gotchas":
With the slide locked back on the slide stop, the barrel is not at the full upward tilted position. The slide can move back further, and does during recoil, so trimming everything with a slide-locked pistol as a guide did not give appropriate clearances and caused the barrel and suppressor piston to touch the chassis. By removing the recoil spring from the pistol, I was able watch for barrel clearance at full slide rearward extension without having to fight spring tension.
I wanted to keep the bottom half of the center cylindrical portion of the blast tube intact and flush with the front of the chassis for aesthetics. I found that it needed to be trimmed back a little from the front edge (seen in the pictures above) or the suppressor piston or flash hider would make contact with it during barrel unlock, causing issues.
Disclaimer: This information is provided for entertainment purposes only. Do not attempt.