Style tags supported by Onyx dictionary app

[Markismus]

I haven't really looked into it, but the same Stardict dictionaries that look lovely in Koreader, look horrible in Onyx Boox dictionary app.

I spend some time tweaking the dictionaries for Pocketbook and Koreader and I am willing to look into an optimization routine for Onyx Boox.
(Results from that script are here.)

Question is: Which tags should be omitted or changed?
E.g. the blockquote tags in the Oxford dictionary, 2nd ed. are horrible and should probably be changed into span-tags.

However, I also see that entries in the Duden 7th edition are spaced very heavily, while Koreader is nice. So span-tags could be an issue.

What would be great: If we could simply (re)write the css that the dictionary app bases it styling on!
(This is the workaround that we use with Koreader, too.)

Does anyone know where the file is that the app bases it styling on?