I did a Google search for "clutch holder tool" because it was time to buy one, finally, after using less than perfect methods to hold while I tightened.
Google search led me to this thread! I should have started here.
Anyway, as others said, excellent idea! I love to save money/ hate to overpay for limited/ single use tools.
I built mine using 2 plates each to spread the stress out a little wider in the hub and basket. Of course, getting them perfectly lined up before drilling is key to success or it won't fit in there. I dabbed each plate with a little epoxy and assembled it into the hub/ basket to be sure that everything lined up, then pulled it out and drilled and bolted once the epoxy hardened and it was properly held in position.
Also, I used 2 stainless eye bolts to use as handles so I can pull the darned thing out of the basket/ hub after using it.
1000 thank-yous to JEC, and here's a pic of mine: