I've been trail running out there for a few years. I've been using this map:
http://www.hikingmichigan.com/PDFinfo/BigLoopTrail....
If racing in the southern park we could use the Bloomer #3 parking area. I've bike thru there on the dedicated bike loop which would be the outer loop of trails.
I've run through the area between sawmill road and fox lake. If I remember it was rolling hills with the legacy trail (marked blue) running from fox lake down to the parking. I'm not sure how big that parking area is. The old gravel pit has ample parking if the DNR opens it up and lets us park there.
The section north of fox lake is awesome. Lots of really nice terrain and fairly good running. I've tried to find a lot of the trails on the map. Some are still hiked but a few are hard to find. I went up as far as Hegel on some of the legacy trails. It gets more open (no trees) the closer you get to Hegel.
The section southwest of Tody Lake is nice with some big pine forests and some decent topography. There is a sweet overlook to the southwest...you can see for miles.
If we used the section north of fox lake we could park at the equestrian campground. Ample parking. There is also a medium size lot on fox lake by the power lines. The best start would be on fox lake directly north of the gravel pit. The road is wide enough to potentially park down the side of it if the DNR allows it. Fox lake is closed from the gravel pit all the way down to the private party. It is essentially a one lane road that the locals use to go mud bogging down.
I have several gps tracks of trails on the north side of fox lake. Igor - would you be able to get basemaps of that section? I'm more than happy to go out there and explore the trails and get them all mapped out.