I've a Lex SV823A with 4 onboard BT878 chips. It seems, however, that I can only set the image size to a maximum of 352x288 when in colour (YUV422 etc.), but I can set it to 528x432 (1.5 times the size) if I use the same camera and set the colour palette to Grey.
I haven't had chance to check whether the camera makes a difference but I very much doubt it as all they're sending is PAL Comp Video.
Has anyone else experienced this?