Sure but you shouldn't be connecting as distinct psuedo-identities during the same Tor session (mentioned in the article); if a custom browser size is associate

Sure but you shouldn't be connecting as distinct psuedo-identities during the same Tor session (mentioned in the article); if a custom browser size is associated with a one-time-use anonymous session then it shouldn't be a problem except that it leaks information about what window sizes are possible on your system, and your custom resize is very unlikely to be random; probably predictably proportional to your actual screen size.