Using Firefox Portable with Selenium 3+ and GeckoDriver

I am trying to use Firefox Portable 60.0.1 with Selenium 3.11.0 and GeckoDriver 0.20.0.

So I specify the executable for both the Firefox Portable and GeckoDriver:

System.setProperty("webdriver.gecko.driver", ClassLoader.getSystemResource("webdriver/geckodriver_0.11.1.exe").getFile());
System.setProperty("webdriver.firefox.bin", ClassLoader.getSystemResource("FirefoxPortableESR/FirefoxPortable.exe").getFile());

The above results to Firefox Portable and GeckoDriver not being able to communicate with each other. However, if I run:

System.setProperty("webdriver.gecko.driver", ClassLoader.getSystemResource("webdriver/geckodriver_0.11.1.exe").getFile());
System.setProperty("webdriver.firefox.bin", ClassLoader.getSystemResource("FirefoxPortableESR/App/Firefox64/firefox.exe").getFile());

It seems to work fine.

The problem is I would like to use the FirefoxPortable.ini to define some parameters are the higher level and have that additional flexibility.

Any ideas would be highly appreciated.

Best
Dio