Thin Client Performance


We have a customer running thin client at Faroe Island and the Acurcl is based on our server in Copenhagen, version 9.2.1 and they are complaining about the performance.

Of course it is the connection, and they have a connection with 20 Mbit Down   and 10 Mbit up , but a slow ping  (around 65 ms). How much does this Ping influence in the performance. I have read about  AGS_RECEIVE_BUFFER_SIZE and AGS_SEND_BUFFER_SIZE but I can't se any changes in performance, when I change these settings. Has anybody got similar problems with slow Ping, and how have you optimized your system.
Is it possible to reach a satisfied performance with such a slow Ping ?
Does anybody know a good way to measure performance in a thin client environment ?
Best Regards