The Necky Chatham 16 is a manoeuvrable kayak that should suit a Flat Earth Kayak sail very well.
Unlike the P&H Delphin, which has a rigid foredeck, the Chatham deck is soft and would not be stiff enough to support a mast foot without some modification. The stiffest area was between the compass recess and a central deck elastic fitting. This was also in line with the deck line fittings, which saved drilling extra holes for the side stays. To make the stays easily adjustable I used Clamcleat white CL266W/R Mini Line-Lok cleats.
To stiffen the deck, I cut a piece of 3" thick black closed mini cell foam and pushed it into place so that it was under moderate compression.
The black sheet and the red uphaul were led aft to a pair of Clamcleat CL 213 and CL214 low profile line cleats. note how the red uphaul is threaded behind the rear deck elastic then forward...
...where it is tied off to the loop formed where the yellow back stay goes through the snap shackle. To lower the sail if there is a strong wind from behind (on a run), uncleat the red uphaul, then pull on the end. This pulls the back stay towards you collapsing the mast. If you rig the Karitek way (with two rear set stays and no back stay) you can't do this and in a strong wind you need to turn the bow of the kayak from down wind round into the wind to drop the sail.