Line spacing changed in recent (last 12 month) builds

[bobMuk]

I installed this driver (great work by the way!) last year and it worked great except for garbage chars after printing images. So I upgraded to the latest version today and images are fixed, but the text line spacing has increased so it's almost double-spaced.
Is there any way to change this? I don't think there was a configurable option on the previous version so I think I had everything set to defaults... and there's nothing I can change in this latest version.
I've also gone through all of CUPS' settings and can't find anything.
Is it configurable at all?
EDIT: looks like this is possibly a duplicate of issue #29

[bobMuk]

So Looking at "set default line spacing" command in the escpos command set:
https://reference.epson-biz.com/modules/ref_escpos/index.php?content_id=20
...I thought I'd be able to edit rastertozj.c to insert the command immediately after the printer gets initialised:

static const char escLineSpace[] = "\x1b\x33";

Note that using the ASCII char "3" caused a compiler error so I've used the hex code instead.
Then in setupJob, immediately after the escInit is sent:

void setupJob() {
  SendCommand(escInit);
  SendCommand(escLineSpace);
  mputchar (8);

Wierdly, with a value of 8 the driver works but there's no change to line spacing. Trying lower values I find that the driver just doesn't work at all - you can send jobs which supposedly print but the printer does nothing.