Hey Clembert,
You did a real nice job with that Harbor Freight bench. Your method of mounting your press on the wood plate and then securing it with the vice is a good idea and may work out just fine for what you do. It is handy to put in place and handy to get out of the way for other work.
Over the years I have found that I prefer something more solid for some of the work I do, but that may not be true for you. If you find you do some sizing or whatever that requires the press to be mounted more solidly, I am sure you can add one or two lag bolts through the plate and into the bench when in use and remove them when done. Also, if your bench tends to come up when raising the press handle, you can add some heavy weight objects to the lower shelf or even bolt the front legs to the floor with angle irons.
Again, you did a nice looking job, your pictures are great, and I hope you have a long enjoyable experience in the reloading craft. Cheers to you, and thanks for showing us what you accomplished.
Best wishes,
Dave Wile