Suppressor Questions

6 days left... and a couple questions.

1. I know there are some great existing designs, but just because we can, I'd like to try to design my own. Does anyone know of some good resources for suppressor design? Anything that breaks down some key design characteristics or helpful calculations/simulations would be helpful. Is there any good sources, or is it kind of down to trial and error?
2. What is the best place to check the legality of the process, assuming you go totally above board. Mainly asking because I would like to know the legality of unfinished suppressor-ish systems like solvent traps, undrilled cups, or a laser cut plate that could be folded into baffles.