Can you combine letterpress with offset (flat) printing or digital imaging?
While we can arrange for flat (offset or digital) printing on the 'B'-side of a piece, we do this only for technical reasons (full-color, heavy solid coverage, halftones, etc.), rather than economic reasons. Due to the costs involved in setup, outsourcing offset printing will add more to the cost of the project than having the B-side printed by letterpress.
Another problem with combining letterpress and flat printing is that we do not know of any lithographer who can handle double-thick stock. Most offset and digital presses can handle stock up to about .015" caliper. Even our single weight stock (110# / 300gsm) is thicker than that.