In my loco kit stash I have an Ace kit for a C1 Atlantic which I plan to build as 4419 when fitted with the booster engine, Gresley cab etc. due to the modifications that I need to make to the kit I may as well go the whole hog and add inside motion.
According to RCTS Part 3A 1419 as was was a standard superheated 4 cylinder engine Further info gleaned from OS Nock's GNR Atlantics book has the cylinders as 20" x 24" which are shown in the chart in CTS Part 3A (page

What I am trying to determine with this post is what type of Stephensons motion are we talking - single slide bar, 4 bar etc.?
I do have several GA's but I am struggling to interpret them. My interpretation is that it's single slide bar with what looks like a curved connecting rod that passes over the front axle but I would appreciate it of someone could confirm that for me.
I would also appreciate it if someone could point me at a reasonable drawing of how it all fits together. I have found the Wikipedia drawing but it doesn't appear to have slide bars only valve guides.
Many thanks for any assistance you can offer.