If you have the double page tiffs you could try the following
I split double page tiffs I get from my scanner with Irfanview
http://irfanview-forum.de/showthread.php?t=4220.
Then I convert the single page tiffs to jpeg, zip em, rename the zip to CBZ, and add the cbz to calibre.
I don't convert the the CBZ's because they're read on a mint notebook or on an android tablet
BR