The best option is to write a letter to the ATF firearms technology branch and get a ruling from them in writing. Anything else is akin to playing with fffire ie. federal firearms felony.
Contact info is here
https://www.atf.gov/firearms/firearm...ion-technology
You'll need to explain exactly what your are trying to accomplish and attach the prints. Answering inquiries just like this is what their job is. Basically you'd be asking for the ATF to rule that your faux can design is in fact not a suppressor under current law. Without the ruling in place you can still conceivably get in a bind. Even without the plastic muzzle plug in place the faux can may still be deemed a suppressor by an LE officer and seized and then sent the the aforementioned Firearms Technology Branch for legal determination.
Once you have the ruling in writing, assuming it is in your favor, You would keep a copy with the "Hush Puppy" set anytime you take it out to play so you have documentation that everything is legal in the event of an inquiry by local LE.
Merry Christmas
Cheers
Bill