DO ftp about 1/4 speed compared with Filezilla

On my local network at home, I usually copy large files (OAM maps, videos, etc) to my phone using ftp, as I have ftp server pro installed on the phone.

If I use Filezilla on my PC to copy large files from the PC to the phone, I consistently get around 580Mbit/s throughput to the phone (a Pixel 6 Pro). If I use ftp within DO on the same PC to connect to the phone and copy the same files, I get around 150Mbit/s max throughput.

DO is v12.25 x64 on Windows 10 x64. Any suggestions on improving the throughput. I haven't changed any of the ftp settings in DO from the defaults - when I search settings for "ftp", this is what is found:
doftp

Try changing the first option there. Larger sizes may be better for fast networks. You'll need to start a new transfer to test each change.

How large is large? Is the value for that setting in bytes, Kb, or what? I tried setting it to 65536, restarted DO, and when copying a 1.6Gb file, got a throughput maxing out at ~140Mbit/s, so slightly slower than with the default of value of 0. I also tried setting the value to 1048576, and the throughput dropped slightly again to ~125Mbit/s. Copy the same file with Filezilla, and back to ~580Mbit/s throughput.

I think 64 KB is the default. Try 5 MB, but the best value will depend on your setup and may take some experimentation.