This is certainly a very different way of running an 11k at an average pace of 6:28/km. All the training programs for half or full marathons recommend some form of intervals. Recommended distances range anywhere between 400 m to 1 mile (1600 m) with a few minutes of walking or easy jogging between repeats.
I'm not sure how/if the garmin 405cx can be set up for interval training, so I just did 1k of walking/jogging between my "fast" 1k's at ~5:00/km. Those slow resting km's took over 7 min, which is probably a little too much rest between repeats.
There are a lot of 4 hour-target-time marathon training programs out there. Finnish running-site "seppola" has these 1k at 5:00 pace intervals. I think Kuehls book talks about up to sixteen 400m repeats at 5:00 pace, while Galloway's program has 4-8x 1 mile repeats at 5:20 pace and Janne Holmen's program (see also here) has fewer long 3-4k repeats at 5:18/km or so.
There's a race in Forssa on Saturday(which I haven't signed up for...yet)