Quote from the Sinar manual, available at Butkus, just for the sake of completeness.

“Specially large lens panels:

(Fig. 29) The SINAR lens panels normally supplied are big enough for all standard lenses for professional cameras. Yet it may happen in very rare special cases that an even larger lens panel is required. This combination is possible through using the rear carrier 5// - 13/18, No. 1610, together with joint block No. x310V as front lens carrier. Here too it is neccesary to use the special bellows No. 2075 from 5/7 - 13/18 to 8/10 - 18/24, as well as a special lens panel No. 810.”

There is an accompanying photo, but the quality of the scan and the original printing is less than stellar. What it shows is an 8x10 back with a reversed 5x7 standard and the above-mentioned bellows. If one would like to use large lenses on a 5x7 with this configuration, I guess one would have to make a new bellows.