Keep it simple wrote:
The most straightforward pacing strategy is to run at an even pace throughout. If you want to break 1:25 in the half-marathon, go out at 6:29/ mile and try to maintain that pace through the finish line. It may not be the absolute optimal strategy, but it's close enough that you shouldn't bother trying to come up with anything more complicated than that.
I like even pace for HM as well (adjusted for hills, wind, etc, of course).
O.P. - with your recent race, you have a great benchmark for your fitness since your pacing was very good other than those first two miles being too slow. Pacing for a 1:25 from the gun sounds like a good plan for your next race if that is your goal.