A little off-topic, but thinking about the possible future of your project: If X11-over-Network turns out to be too slow, you could experiment with starting a virtual X11 with a VNC server, then open a VNC client on the user terminal (you can possibly pipe that all back to the client using the existing SSH session via port forwarding to even make it secure).

Using VNC (or something similar) can be orders of magnitude faster, depending on the use case. VNC sends you a compressed screen update for the parts ofd the screen that have changed (depending on the selected VNC algorithm). On the other hand, worst case case for X11 is that it sends you pixel-by-pixel drawing operations.

As an additional bonus, if you ever need to generate screenshots of all .vcd files, you could just call Net::VNC instead of the external VNC viewer to automatically capture a screenshot of the application.

Also, if you ever want to port your project over to a browser, you could use noVNC to just view that application from within a webpage. In theory then, the operating system of the user wouldn't matter at all anymore, because ALL the software runs on the central server and all the client needs is a web browser that supports websockets. (So, basically, every browser made after about 2015...).