Thanks all for input so far. Yes, TT, tuning at 30m.
I think what I maybe didn't convey in my earlier post is the difference in final NP height between the same shafts (albeit one spine different and a tad shorter) but with different nocks. So I've tested this just to make sure I'm not imagining things by changing the nocks on the 410s for the over nocks and I end up with a higher NP again. This is
Beiter hunter nocks Vs
Beiter over nocks.
So my question isn't so much about relative positions of bareshafts to fletched shafts, more the relative positions of the same shaft with different nocks. Boiled down, let's say I've shot six identical bareshafts, three with hunter nocks and three with over nocks at 30m. Obvs the total arrow length with the overnock is slightly greater (original reason for trying them is to get a longer overall arrow).
I seem to end up with a high NP anyway and I realise tiller, bow hand position and finger pressure all have a part to play. The over nocks just seem to make it higher.
If that's how it ends up, that's okay but I wonder if the slightly longer nock (and therefore slightly greater overall length) could be that significant?
It's all relative to my hand position, my bow's tiller and my finger position but for reference, with the hunters, my NP measured from the arrowrest, is around 12mm to the bottom of the top nocking point and with the over nocks it is heading towards 16mm with my usual bareshafts and fletched together in gold on a frostbite. Also longish (32.5") draw.
I'm not losing sleep over this, I just wondered if it was something anyone else had noticed or whether it might be form/technique related. If "they all do that, sir", then I'll set the higher nocking point and crack on. If the over nocks are somehow unforgiving and showing up a technique issue, I can work towards improving matters.
Thanks again for the input and sorry if I wasn't overly clear earlier.