Dimitrii, I think most of the guys who have commented are well-aware of matching a rod to a line class. The Nirai, if fished with sensible angles, is appropriate for PE8. Few anglers can fish the heavier jigs rods like a Spinoza 5120 effectively.
I have tested the sink rate of PE8 versus PE6 for depths of 80 to 120m quite a bit when fishing for samsons in Perth and there really isn't the difference you may think. I appreciate it might be more noticeable if using small jigs like say 120-150g but when you're using 300 - 400g jigs, the difference is minimal.
Brandon,
I think my poor English made you misunderstand me. I do not doubt that most of the guys reading this forum well-aware of matching a rod to a line class. And, of course, Smith Nirai is appropriate for PE8 (as I said, I used this rod with PE8. And tried different angles with it with very high drag rate). My point was that rods are very different within the same line class specification. And by my opinion, saying that the fact of using PE5 (or any) on dogtooth itself guarantees it will kill the fish is not correct unless you specify the certain rod model.
For example, compare two cases: Sevenseas Northern Mariana Extra Dogtooth 100 with PE5 (or better PE6) and Smith Nirai with PE8. I bet one will land 50kg dogtooth faster with the first set up than with the second.
As for the jig weight difference, I have the the same practice with Dan. I noticed that PE6 can be fished with 250g or sometimes even 220g at 100m while PE8 can not.