Thanks knc1, fred_be9300. I have updated my Klingon guide
which can be grabbed from a spoiler on the OP to v0.4. The contents has not changed other than trying to enable proper cover view (on the Touch and PW) by
1- Creating a 180x240 thumbnail from the 600x800 cover
2- Adding the thumbnail metadata in the .opf
3- Kindlegenning
4- Using MobiMetaEditor to add a fake¹ ASIN=B000KEB6WW and CDEtype=EBOK in additional EXTH (113, 504, 501) records.
I didn't test, not having these devices. Let's call it tentative until someone reports results.
[EDIT] Ah well, didn't work :
lex1000 tested it
¹
This ia a real product ASIN, which I selected to insert more easily the metadata, it is just not one for a book.