yes the piston does moves slower closer to TDC but if the piston hits the stop at the same distance on either side of TDC(& halfway between the contact points is showing TDC on the marks) I wouldn't think that it would be more accurate if you started further away imnho but if I am wrong on this then I definitely want(need) to know.EDIT after some thought yes 5 is going to be in that dwell area so further away(maybe at the edge of the tab on each end) or farther is correct. Thank you for the enlightenment.