AFAIK, what you need is:
this in your init.sqs
// Initialize spectating script when player joins as seagull
// Set the following to limit visible sides:
// KEGsShownSides = [west, east, resistance, civilian];
[] execVM "spect\specta_init.sqf";
Sleep 2;
foo = [player, player, "null"] execVM "spect\specta.sqf";
This on your onPlayerRespawnAsSeagull.sqs
; Initialize spectating script when player dies
; Set the following to limit visible sides:
; KEGsShownSides = [west, east, resistance, civilian];
_this execVM "spect\specta.sqf";
This on your description.ext
// Include spectating script resource
#include "spect\spectating.hpp"
And the spect folder.