Please recheck your Firefox version and try to add it again. Version 0.4.2 should also run with Firefox 52.4.1

The former versions faked the transparency always. But since this channel is treated differently by the browsers I think it is saver to not fake it. It does not affect the security.

Regarding the missing options: only these options are displayed that are useful with the other selected options. The mentioned "ignore the most frequent colors" is only displayed in expert mode and when faking the read API.

For the default random number generator I ask you to open an issue at github. This has to be discussed in more depth. I myself are not sure what the default should be.

You're welcome.