Questions about YUN2 shield

Official Hardware Classic Yún
1

Hi guys,
I have a couple of questions about a shield I want to build for YUN v2.

Requirements:

  1. 1x RS232 serial port
  2. 1x CanBus interface.

My idea/questions:

  1. Since RX/TX can't be used on this board (reserved to Atheros chip UART), I'm planning to use a MAX3232 chip to interface D8 for RX (this should support change interrupt) and D12for TX using SoftSerial.
    Do you see problems? Max speed required 57600bps

  2. CANBus - I have already used MC2515 based circuits before, will the ICSP port available or is it also used exclusively by the Atheros chip? (I can see they are connected, not sure if they're reserved)
    If I can use it, what line should I use for CS -> SS. On UNO I would use D10/SPI_Slave, on the MKR shield I see D3/PA11 is used, but on YUN I can see this pin (PB0) is not exposed and used by RXLED.
    Any suggestion?

Cheers and be safe.