can this be adapted?

I bought the wall plate and swivel arm shown below, anticipating the 5/8 hex stud to fit into the 5/8 baby receptor. Just goes to show how little I know about adapters. The hex shape of the stud does not allow the two to fit together. Fudge.

Suggestions on how to get this to work? My goal is to mount the plate overhead between my joists and attach a magic arm (to the other end of the swivel arm) which will eventually hold a strobe with a small Nova softbox.

I already mounted one light in a similar fashion using a Kupo monitor adapter stand. Although not designed for how I am using it, it works like a charm. Only problem is that no one has any more....and they are on backorder everywhere I call. I even called Kupo and they had none. Hence the reason I conceived my alternate solution, which proved to have a major gotcha.

It looks like you should be able to cut the most outward hex part off, or i see a tiny copper pin that might be able to disconnect the forward hex?

If you have the option to return the parts and can't figure it out, this is how i would of done what you're looking for: