I closed the rear slider bow slightly, then refitted the plexi and skirts. The clearance between the rear bow and pins from the fuselage is only about 16th of an inch each side, so bending the bow or the pins further in isn't an option. The skirts widen the canopy frame as they engage at the front, so I angled the entrance to canopy hooks to guide the pin into place. Everything works as it should and the slider track is perfectly centred .... yay ... persistence makes ... the canopy a very big job !!