Good points. I think sharkfins must also slow down a spear - and I would think all ET spearguns require sharkfinned spears.
Sharkfins probably hit the fish harder though and cause more damage. The jury is still out on whether they are really stronger than notched spears (see discussion of Cressi spears breaking at the sharkfin welds

).
If they break at the sharkfins it’s likely because the weld itself changed the temper/hardening of the shaft. I am fairly sure that’s why Salvi has experimented with what I assume is a less intrusive weld method on their new Capture shafts where they use robotic laser welding. The bead is much smaller but seems perfectly placed.
I’ve only had one of these shafts and it’s not a big data set but still, I’m recommending it widely, haha.
The sharkfins on those shafts are also as small as they can be (3mm tall) and they are finished well, too. It’s the only shaft I’ve had that didn’t need deburring.
Now, 3mm may not be tall enough for enclosed tracks but then again, I don’t need ETs and trust the experience and tests done by Majd showing their performance loss.
Look for his Pathos Sniper test on his SpearQ8 YouTube channel where he ends up grinding the ET off of a brand new gun
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