Automotive book publishers

Since I'm close to finishing the first draft of a book on cars, I'm trying to think of which publishers to contact. And looking through Writer's Market, it seems that many of the bigger names in the field like Bently Publishing or MBI pay royalties off the net. I haven't been able to find the information about how the two biggest ones, HPBooks (a Penguine imprint) and Cartech, pay. Is paying off the net standard practice in this area, just like publishing in paperback with a 8x11 trim size?

Thank you. I'll see if I can hold out for a publisher that offers standard royalties, then.