You are half way there by using a commercial registered office in Washington State, which is common place and meets the primary requirement of providing a physical address at which legal process such as a summons commencing a lawsuit or a legally required notice can be hand delivered.
While Washington State does not allow for a mere private ...
The FAA regulates amateur model rocketry under 14 CFR 101, Subpart C.
For a Class 1 model rocket:
(a) Class 1 - Model Rocket means an amateur rocket that:
(1) Uses no more than 125 grams (4.4 ounces) of propellant;
(2) Uses a slow-burning propellant;
(3) Is made of paper, wood, or breakable plastic;
(4) Contains no substantial metal parts; and
(5) Weighs no ...