OOOOOOOH I see what you did. Their's some official tags and ID's you could be using for this. Hercules doesn't have it in their skill_db.conf or other files needed but you can add it in yourself. Here's some of the missing tags and ID's from my emu...
// Soul Linker 2 / Soul Link Enabled
572,9,6,16,0,0x1,0,5,1,yes,0,0x200,0,magic,0, SL_DEATHKNIGHT,Death Knight Spirit
573,9,6,16,0,0x1,0,5,1,yes,0,0x200,0,magic,0, SL_COLLECTOR,Dark Collector Spirit
574,9,6,16,0,0x1,0,5,1,yes,0,0x200,0,magic,0, SL_NINJA,Ninja Spirit
575,9,6,16,0,0x1,0,5,1,yes,0,0x200,0,magic,0, SL_GUNNER,Gunslinger Spirit
//576,0,6,4,0,0x1,0,1,0,no,0,0x8,0,none,0, AM_TWILIGHT4,Twilight Alchemy 4
//577,0,6,4,0,0,0,1,1,no,0,0,0,none,0, DA_RESET,Dark Optimize // (Skill level and settings guessed based on DE_RESET)
//578,0,6,4,0,0,0,1,1,no,0,0x8,0,none,0, DE_BERSERKAIZER,Berserkaizer
//579,9,6,1,0,0,0,1,1,no,0,0x8,0,none,0, DA_DARKPOWER,Dark Soul Power
These exist in official but arn't used but you can take advantage of them. I know the soul link animation works for all 4 of these spirits. Try switching everything over to 575 SL_GUNNER.