With my machine i can print at 100 mm/s however support material towers wobble at these speeds. If i change the settings such that there are multiple process' and that every 10 mm (10->10.2, 20->20.2...) it prints support with 100% infill. This solidifies the support towers and keeps them attached together.
If there was an option to have the supports print a solid layer every x layers that would be great ( Like the "Include solid diaphragm every "x" layers for the infill)