The AP1s I've just ordered are the same configuration I believe Gareth. Can you notice any difference between +1/64 and standard? I have little girl hands is all.
Like so many things, it depends.
If you've played a standard install grip for a good while, then switched to a bigger/smaller grip, you will notice the change. Likewise if you played midsize and moved to standard.
With me moving from 1/32" oversize to 1/64" I don't notice the difference so much. After all the difference is equivalent to around 1-2 layers of tape.
If you were to take a standard install (0.60 core on a 0.60 shaft with 1 layer tape) then it takes one additional layer your grip would be 1/64" oversize. Add another 2 layers and your grip is 1/32" oversize.
As an aside 0.58 core grips have more material in their manufacture so tend to feel a little thicker any way. This is why when you add a 0.58 core grip to a 0.60 but shaft, the grip is automatically fractionally (1/64") oversize from standard.
Certain grips are also thinner between manufacturers. Sharpro feel paper thin, where Lamkin feel much, much thicker.
It's also worth noting that no all iron (... Or wood) shafts have the same butt diameter. Some wood shafts run at 0.62 which changes the dynamic again 
Sorry I can't give a more exact answer pal, but I will say if your irons are stock with the XP95 shaft and the Titleist Velvet grips, your grips will be 1/64" oversize :thup:
