If you can get them, I'd try some Peavey Cirrus Bass strings. I have some on a Peavey Cirrus bass with rear string-through, and I have about 22mm of full-width bass string past the nut bottom E, with more length on the other strings. Though the Cirrus is supposed to be 35" scale, mine measures at a 34"scale. It's 35" from the fretboard side of the nut to the string-through hole on mine.

Your string-through ferrules appear to be only slightly further back than mine, so if the body isn't too deep (which will add to the overall string length required) you should probably be OK with them.