Ground plane and image target

Hi all, what I'd need to do is use an image target (the image target itself will be on the ground) to set where the AR models will spawn and then lock the models to the ground using the ground plane, as extended tracking isn't accurate enough (at least for my hardware limitations). Years ago I found something that helped quite a bit on the forums but I can't fix it to work with new vuforia versions.

Thank you and sorry for my broken english.

Edit: using latest Unity and Vuforia versions.