FMS14 now offers considerable better performance with WebDirect then was the case with FMS13.
FMI used to recommend 256mb RAM per WebDirect User Session under 13.
Now WebDirect under 14 requires an average of just 32mb RAM per session.
So this means 3 WD users per 100mb spare RAM and 30 users per GB spare RAM.
Remember that the RAM used by WebDirect is from the RAM not allocated to FMS Cache, so don't make your FMS cache too large, and leave enough for the OS and WebDirect.
I attach a small spreadsheet with the numbers from my testing.