After much hacking and some very good pointers on RCGroups (esp. TeroS) I've finally managed to get the DS-16 doing what I want for IMAC flight
Mainly this means stick activated snaps with hysteresis (where the condition is exited at a different, lower rate than it was entered at so you can unload elevator during a multiple snap without condition changing). I thought it might be useful, so my design spreadsheet is below.
L9, L10, L11 are used to switch three flight conditions for different snaps
L13 is used to switch a stall turn (hammerhead) condition.
All the other switches are doing the hard work of the logic in the background!
My radio is mode 2 so THR = P4, RUD = P3, ELE = P2 but you could sub these easily for different radio modes. (C, P) = Center, proportional. (C, P, R) = Centre, proportional, reverse) ...
I'd be interested in any feedback, especially from seasoned IMAC pilots
The image look a bit blurry, so I've attached a better quality PDF too with it in.