Hi GaryI think I am releasing post MCL but as soon after as I am physically able. As soon as I sense (imagine?) the rod butt has begun to unload, I open the fingers of my line hand.
Because of the lag time between rod unloading signal capture - brain - opening fingers can be about 80 ms (40 ms in each way), you are likely releasing pre RSP or close to RSP. You say that it corresponds to peak haul velocity also (halway of haul approximately) but are you sure that your peak haul velocity does not correspond to the maximum load of the rod (MCL)?
Merlin