When you use DBF, your application must transfer a lot of data to the workstation. Multiple VPN's will surely slow this down. Remember, in this mode you are using Microsoft Windows Peer To Peer networking which is not robust.j
If you have Advantage Database Server ( not the LOCAL version, but licensed remote ), then the data processing takes place at the server, and only essential data is transfered across the VPN. This is normal Client/Server technology.
You can get a 30 day free trial of Advantage Database Server. The only modification to your code will be in the MAIN( ) function where you make the RDD available.
I have clients who use this method and speed is not an issue. Since you can try it at no cost, you might find this to be the better solution.
My startup code reads from an ini type file to know if it should use RDDCDX, or RDDADX and if it is Remote or Local mode.
We done this for the past 20 years.
Tim