I can draw quite a few parallels with your results, in my little old HW50 I too find 8.44 exacts to be down on power, for instance I can get 8.64 FTT shooting 775fps where the exacts are around 720!
Best groups for me were FTT (back a few years ago where the QC was much better than now) supremely efficient and the shot cycle is superb.
Now I shoot exact RS, I still hanker for FTT but I cant be arsed to size them
superdomes, I've yet to find a springer that superdomes feel nice with. the shot cycle seems almost percussive, even if they group they just feel horrible