Sideband POST connection in irule

Hi

I'm trying something very simple. I need to retrieve the result of a POST to a web server. The following curl command on the F5 returns data i need:

curl -X GET http://192.168.153.11/trusted?username=admin

in my irule, after the initial sideband connection is established, i've tried many variations in POST to get it working but keep getting a 400 response form the server:

set data "POST /trusted?username=admin"

set data "POST /trusted\r\nContent-Type:application/x-www-form-urlencoded\r\n\{\"username\":\"admin\"\}"

and a couple more.

I've been scouring the interwebs looking for a sample but found a few posts with a similar issue.

Can anyone assist?