For info, my VivoBarefoot Neo Trail shoes (4 mm lugs on a 2mm sole) just took me round a VERY muddy North Downs Run (30K) over mud, grass, road, mud, chalk (with occasional flints), fields, cobbles and more mud (sticky mud, sloppy mud, watery mud - all sorts of mud!) just fine - including lots of downhill and lot of uphill sections. Also were fine for 25+ miles along the North Downs Way, Farnham to Dorkimg, last weekend, including tracks, sandy sections etc.