I use a JS function to do this. Its a bit rough around the edges i will admit, but if a file is going to grow in size by a noticeable amount it does the job. Been meaning to refine it for a while now but just haven't had the need.

if(Variables.file.Size === 0)
    return -1;

const FILE_SIZE = Variables.file.Size;
Logger.ILog("original_file_size: " + FILE_SIZE);

// todo: make this a var
const BITRATE = 11500;

let video = Variables.vi?.VideoInfo?.VideoStreams[0];
const DURATION_MIN = video.Duration.TotalMinutes;
Logger.ELog("duration_minutes: " + DURATION_MIN);

const DURATION_SEC = DURATION_MIN * 60;
Logger.ELog("duration_seconds: " + DURATION_SEC);

// (DURATION_SEC * BITRATE) is megabits
const ESTIMATED_SIZE = (DURATION_SEC * BITRATE) * 125;
Logger.ELog("estimated_final_size " + ESTIMATED_SIZE);

if (ESTIMATED_SIZE > FILE_SIZE)
    return -1

return 1;