I have a few Riffes Hawaiian shaft, this is what all have in common, and I read somewhere too ( forgot man ???? ) that this is the way it should be :
When on a horizontal plane, the flopper ( if Hawaiian ) should sag down some 45 degrees. My floppers also open up only like 70 degrees or so. The last travel of 45 to 70 degrees must come with some resistance and when u open up to maximum, the flopper must remain open cause of that resistance/friction. The idea is to make sure the flopper remain open after a fish has struggle pushing the flopper open.
If ur flopper can not maintain its open position after u pushed it to maximum angle, u will loose more fish because a fleeing fish that goes up/surface will cause the flopper to shut close under its own weight ( plus water drag ) and thus ineffective. This is also the reason if you shoot a fish and the shaft say protrude say some 7-8 inch on the other side of the fish and the fish has not tighten the shooting line on you, u need to give a quick tug to the shaft. That tug will open up the flopper and placed the flopper on the fish skin.
One way to test ( my version
) a Hawaiian flopper is simple.
Hold the shaft horizontal with one hand, grabbing the rear part. Let the flopper open up as per gravity and its own weight. Use your other hand to tap'slap hard the middle of the shaft to cause wobbling on the shaft. If ur flopper is set correctly, it will be opened to maximum ( 95% of maximum, actualy ) and remain open even if you whacked ur shaft again and again. This wobbling effect mimicks the fish struggle as it tries to free itself from ur shaft and that is the fall, cause the flopper opens up....Viola
I think the resistance adjustment will not be at the pin. It will be at the "U" fold of the flopper, top most, where the hole for the pin are. In my 8mm Hawaiian shaft, it carry the same flopper of the 7mm. What Riffe did was to grind down the area where the flopper will make its opening/movement near the pin. I guess the flopper is more for 7mm shaft and at 8mm shaft, some modification on the shaft surface itself is needed.
I seen my friend using a "loose" flopper loose fish as the sky rocket upwards. Check ur flopper.
60-70 degrees is OK. If any Hawaiian flopper can open 90 degrees, it will be weak when whacked by a big fish. There is not enough metal surface on the flopper to resist the high pulling pressure. I don't know how to describe the term in English. Basicaly, it will be easy for a big fish to do a 180 degrees on your flopper, unless there is a recess on the shaft itself to lock the flopper not to exceed 90 degrees. Look at the Riffe regular screw on large spearhead with two floppers, it does 90 degrees for both floppers but it has a special recess to maintain a "lock".