I've installed slotted flaps on a few airplanes, always using offset hinge line for motion.
I've been considering how to do the flaps on a tracked system for an giant A-10 I will be building, maybe next year. I'd love to see specifics on how folks are building tracks & avoiding jams. There is big potential for jaming of the flap tracks if the flaps get a little sideways during deployment or if junk gets in the works.
I also was thinking about the jackscrew system, but just using a servo divorced from it's pot to drive the screw. Here's an exaple of that being used to pivot a turbine engine on a VTOL model:
http://www.corpcomp.com/weeks1/Rig/Moter_moves.html
FWIW- I think use of titanium on model hardware is more trend than science. It just isn't a big benefit vs the cost increase; discuss...