Negative splits rock

Met up with some people this morning at umstead park for a run. Didn't know how far, or how fast, but didn't really care. The plan was to just run how I felt. It was cold. 43 degrees and I had shorts and a long sleeve shirt and a fleece sweat shirt. Started off with the faster group. I told them I was going to run with them until I warmed up, then slow down to go with the slower group where I belonged. It was cold and windy, but they were doing 8:30 pace so I warmed up quick in about 5 minutes. I was feeling good, but 8:30 is not for me in the park. So the other group was doing about 11 min pace, a little too slow, but they turned around after 30 minutes and I kept going to the 3 mile mark.
first 3 miles 31:54 / 10:35 pace.
then I turned around and decided to negative split back in hopes to catch back up to the other group before they got back. They had a 1/2 mile head start but I figured I would catch them with a tempo run down the hill to the spillway.
tempo run
1.84 miles 16:38 - 9:03 pace.
Then I hit half mile hill, they had just started up, so I passed them early on. But I didn't want to slow down since the speed was feeling good.
1/2 mile hill
.54 miles 5:40 - 10:26 pace.
At the top I didn't stop and just kept going. It is still up hill to the parking lot where we started, but I wanted to get there by 1 hour to make a 10 min pace for the run so I kept pushing.
finish stretch
.62 miles 6:01 - 9:48 pace.
stats for the whole run
6 miles 1:00:14 - 10:01 pace