I figured it out with the help of my friend. What you would want to do is avoid using FormUrlEncodedContent(), because it has restrictions on the size of the uri. Instead, you can do the following :
var jsonString = JsonConvert.SerializeObject(post_parameters);
var content = new StringContent(jsonString, Encoding.UTF8, "application/json");
Here, we don't need to use HttpContent to post to the server, StringContent gets the job done !
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