Creating Slingloads in fsx se

Hi all

I'm new to the forum so let me start by saying hello
I have being simming since fs2000. My current sim is fsx se.
I have built a full scale MD500E simulator (my favourite helicopters) with T shape instrument panel and dual controls using authentic MD500 flight controls .
I'm trying to breathe some life into my fsx se and my helicopter cockpit by adding liftable objects. I have looked at the early Slingloads in the Sandbox liftable missions which was done along time ago
I have object placement tool installed and working and I have built a small heli base

I found an old post regarding*Slingloads here at SOH* and in the post it mentioned* the following method

There are four basic steps:

[1] Select an FSX 'liftable' object from the fsxp mission objects*HERE. Typically these have a hook 'eye' for lifting such as the MIS_top_secret_crate.

[2] Place the object using Object Placement Tool' and save as a 'Mission'.

[3] Save your flight where you'd like to start from to pick up the load and

[4] Equip your Helo with a sling by editing the saved flight file.

I have followed the instructions and I have a xml file that appears when I save as mission but I can't get it working and not sure if I have missed a step

Regards

Rhys