The LC and LC+ Engine knuckles are NOT actuated by an STC, RCS, UCS, 1019, 6019 or similar special tract sections - they are only operated remotely by a remote (physical or software) if equipped. The knuckle design only requires one open/operational knuckle and a fairly straight shot. You can use an uncoupling track to open the knuckles. If the footprint of the uncoupler track matters and you are not using coil operated knuckles, your best and most cost effective bet is to locate these O-27 track sections and cut them to size. You can remove the O-27 pins and use O pins in the rails and it will match right up with O track just fine.
