This is the same setup as I have and the issue with 240 hubs is the disc is too far away from the caliper groove. The 260 hubs gives the disc an extra 9mm back towards the caliper and it all lines up perfectly.
Can you fit a machined spacer between the 240 hub and new disc, then use longer bolts to secure to the hub face? Would this be safe, I'm not sure.
260 hubs are the easiest and everything bolts straight up, but they seem to be hard to get. What about a disc with 9mm more hat height but same diameter?