But it would be super simple to machine an adapter for the front sling and pic rails.
All you'd have to do is get a small piece of aluminum rod and turn it down to the proper outside diameter as a 12 gauge mag tube, mill out the inside the diameter of the 410 tube. Run it through a bandsaw to make a clamshell out of it.
Then they could use the same tri-rail for all of them. I'm assuming the 20 ga mag tube may be a slightly smaller diameter too? If so, the same thing could be done for it. That would make their shockwave parts cross-compatible with all of the calibers by purchasing the shim adapter you need separately.
We have been able to make a prototype adapter for the rail system to fit a 20 Ga. Sent it to a customer and it seems to work great for him. If anyone out there is looking to get one of our rails for your 20 Ga. before we release it as an option on our site, let us know and we will get you hooked up in the meantime!