What do you normally have displayed on the screen during training?
I'm trying to setup a specific racing screen, and tested it in my last HM but found it slightly confusing as it wasn't what I was accustomed to. So it may be worth sticking with what you know.
What I've got on the racing screen is Avg Pace for current lap, Avg time per lap and I've also added the lap counter. The idea being you press the lap button when you pass a mile marker, and you can see whether your current lap pace is on target, and the avg time per lap shows whether your ahead/behind schedule for the whole distance. I added the lap counter as at my last race I missed a few mile markers, and couldn't remember if I had to press the lap button once or twice when I found the next visible mile marker.
For your setup, I'd be tempted to put HR on the second screen as it can vary under race conditions (adrenaline etc) and replace it with Avg Lap Pace (maybe set auto-lap to 1 mile, or 0.5 mile as KingKenny suggested).
Also just be aware that "garmin" distance is normally slightly more than "race" distance (i.e. 1mile on the Garmin is 0.97 miles in the race), so you'll end up running more than 5 miles according to the Garmin.