Double redirect

I have changed my domain before, did 301 redirect, submitted it into WT.

Now I will change the domain again. What should I do with the previous redirect? Should I leave it or to point the most original domain directly to the new website?

Point it to the new one. Doing a 301 -> 301 -> Page is a waste and it will all be transparent to the search engines. For any users it will also be a pain dealing with those redirects.

sitea.com (301) -> sitec.com
siteb.com (301) -> sitec.com

Well maybe I am doing something else than guys here do. This is nothing related to blackhat seo google penalising etc, this is to protect my domain against seizure.

I put a lot of effort to bring domain A to #1, then - to protect the domain - I redirected A to domain B, which ofc is now still even stronger #1 for that kw. Everything is crystal clear to Google: imagine this problem as doublerebranding.

I still think the solution you proposed is the better one, but I want to be assured, since this would be really a mess. Thanks a lot.