Happy New Year!
Linux Laptop <-> TM-D710E <-> 439.875MHz <-> SCS-PTCIIex <-> FT-847 <-> Linux Server.
At both sides, the serial ports were running at 57,600bps. I configured both sides to use 9600bps over the RF connection, I used settings of txdelay 100ms, Paclen of 255, maxframe of 7, mtu of 1500, mss of 1460, and tcp window of 2920 as suggested here. Other settings were at their defaults.
I started an FTP download of a (roughly) 1.6MB file from the Linux Laptop to the Linux server, and about 74 minutes later, it completed. I then downloaded the same file and approximately 70 minutes later it finished. A quick comparison of the md5 checksums showed the file to be ok. During the transfers, it seemed to me that the 710 was a bit ‘slow’ in switching from receive to transmit (compared to the PTCIIex which was almost instantaneous).
That said, given my very limited experience with 9600 baud packet, I still think it is respectable, though more testing is needed and I would welcome any suggestions for different parameters to change.