HI Darrell!
My email didn't alert me to your message!
I have a Garmin 110 which doesn't allow route uploads, so I won't be able to accurately track my pace, but I have an idea now what speed I need to roughly keep at to get in at under 4.30. I wish I did have a 405 though! I am planning to start very slow, at 11 min miles then build up after 3 miles and try to set my pace from there. Whether I can actually stick to that plan is another matter!
It's a shame I can't view your mile splits, just your average pace over the marathon. Elevation wise looks like there won't be any major hills to climb. Just have to watch not the speed up too much when on the downhill parts I think!
Getting very nervous now, and I think I'm coming down with something too which isn't good timing.
Best of luck with your sub 4 - that would be an amazing achievement.