Updating custom fields in Zoho Projects

Updating custom fields in Zoho Projects

Hi

I am wondering if anyone has experience with custom fields in Zoho Projects. I am struggling to update the field using either deluge or the api endpoint. 

My code is:

//custom_Map = map();
custom_Map = {"UDF_DOUBLE_1":"0.27"};
update_Map = map();
update_Map.put("custom_fields",custom_Map.toList());
info update_Map;
// update_Task = zoho.projects.update("mcconaghyboats",project_ID,"tasks",task_ID,update_Map);
//  Make the API call to update the project
    resp = invokeurl
    [
        url: "https://projectsapi.zoho.com.cn/restapi/portal/mcconaghyboats/projects/" + project_ID + "/tasks/" + task_ID + "/"
        type: POST
        parameters: update_Map
        connection: "zoho_projects"
    ];
info resp;


I have tried a number of different ways using both the internal connection and the api endpoint. 

Does anyone have the correct syntax?

Thanks
Carl