Prebend only applies to...prebend rigs...the Hobie runs the old "soft" rig...spreaders are not swept aft enough to make diamond tension bend the mast in the long axis (that's what a prebend rig does).

So, you adjust diamonds to control/limit bending in the short axis.

Get Rick's book...Cat Sailing for the '90's (available on this site's webstore). There is a detailed section on soft & prebend rigs and how to set them up.
Any newer books/video's will not cover the old soft rig setups...they are so 1960-1980's :-)