Re: Low profile work holding
If you have a lot of these to do, it might be worth building a vacuum fixture, with interchangeable fixture plates. We made one for handling small thin parts like this, if this is something of interest to you I can provide pictures. Uses a cheap vacuum pump from Harbor Freight.
If there are any holes through the part that can be used as screw holes, then screw it down to an aluminum sub-plate.
Given the final thickness, I might start out with 5/16 or 3/8 plate. With 3/8 plate you should be able to do all the work in a vice with step jaws.
Jim Dawson
Sandy, Oregon, USA