Have you seen or heard about the rigging failures with the 26M? May want to check into that first.
"The manual states the main sail replaces the back stay." I don't get how this works...
I'm sure your side stays are set back further than the 26X/D/S.
That is what allows no back stay.
I don't think there would be a problem just flying a big genoa if your rigging is tensioned properly.