See the full list of speeds available in MatterControl here: http://wiki.mattercontrol.com/SETTINGS/General/Speed
As you'll see, there's not a specific setting for the layer above the support material, but perhaps one of the other speeds is the one you'll want to adjust for the layer you're having trouble with.
I could take a closer look if I had the G-Code. Can you share the .gcode file? Use Dropbox or Google Drive and share the URL.