Size limits on stringstream for embedded

Keen to use stringstream on an STM32 for handling data that gets sent over various UART connections to radio modules (wifi, BLE, Zigbee, etc). I am running FreeRTOS, if that matters. Very concerned about the dynamic memory allocation in the STL lib causing unhandled overflows (I have to have "-fno-exceptions"). I can handle buffer overruns myself in a simple writer method, so that isn't an issue, but I want to be certain that the stringstream never tries to increase it's memory beyond a pre-set limit.

Currently I just use char* buffers, but, I want to find a better solution.

I want to be able to do something like this.

#include <sstream>      // std::stringstream

class Wifi
{
public:
    std::stringstream* ss;

    Wifi()
    {
        ss.set_max_size(1024); // 1kB
    }
};

TIA