Now the playback window is capable of vastly quicker sending of frames.

Use the burst setting and crank it up. Set the time interval to around 2ms and the burst to 6 and you'll be slinging frames like crazy.

serialworker.h

@@ -50,6 +50,7 @@ public slots:
     void setSerialPort(QSerialPortInfo*);
     void closeSerialPort();
     void sendFrame(const CANFrame *, int);
+    void sendFrameBatch(const QList<CANFrame> *);
     void updateBaudRates(int, int);
     void stopFrameCapture();
     void startFrameCapture(); //only need to call this if previously stopped. Otherwise it's the default