that 30-sized reel was being used to prove a point a month or so ago. It was at the very edge or beyond its suitability for kingies. The session before that one, but still using that reel, I was spooled, quite convincingly. On the kingi in that pic above it took me down to the last 10m of line. So, I got lucky. Very lucky.
Have since moved up to a 55-sized version of the same reel for more breathing room (about 300m of braid on it). If my choices were the 6000 or 8000 sized Okuma Avenger baitfeeders, I'd not think twice about buying the 6000 sized model, even if the 8000 is only $10 more. Extra line capacity when there's enough on the 6000 anyway, is like a match on a raging fire - pointless. You also don't get any extra drag capacity and it's heavier.
But if you were predominantly or always fishing from a boat and drifting livies down to 150m pins then the extra line capacity of the 8000 might be worth it but in that scenario the drag isn't enough for my liking anyway so the reel kinda excludes itself on that basis.
But that's just my thoughts and everyone differs.
Please do let us know how you get on with it, and good luck.