So, finally getting somewhare with it. The problem i was having does seem to be related to the Cargo Indicator not showing due to where its being positioned when i hit the keybinding.. i.e its somewhere, just not on my screen. Found an old post with some creative google searches and found someone who had a similar issue with the controller indicator. So, using that logic, i applied it to the CH47..
In the file location. dcsworld\mods\aircraft\ch47\cockpit\scripts\cargoindicator - cargoindicator_page.lua
There is a line that reads... base.init_pos ={aspect-box_width,1.0-box_height}
I then opened dcsworld\mods\aircraft\UH-1\cockpit\scripts\controlsindicator - controlsindicator_page.lue
Found the line that reads... base.init_pos = {0,(1 - 1.3*size)}
Copied the whole of that line and pasted into the CH47 carogindicator_page.lua
Actually found a much easier solution:
Open file.... dcsworld\mods\aircraft\ch47\cockpit\scripts\cargoindicator - cargoindicator_page.lua
Edit line that reads... local aspect = Lockon_Options.screen.aspect
Change to local aspect = 1
Save restart DCS..
Fired up the instant action sling load operation mission and as soon as the cargo red smoke released, the green hover box was visible!
It now shows the green box with the "All Cargo" option in the comms menu. But i use CTLD and have cargo spawn in front of me - then it still does not show up.
Not the end yet.. Where as this moves the green box, the moving circle, red dot and the height bar are not in the green box, so a bit more playing around to get them into the green box
Hopefully this might help others. For reference, this was the post that i found that got me on the right track - Last post from Slicker55