daboone wrote:OK how does adding any mounting system make a press more stable than direct attachment to a rock solid bench?
Your operative description was "rock solid bench". If you already have that, one reason a person might want the Lee Bench Plate System is the versatility it offers in quickly changing out presses for people with limited bench space. I kind of fit that category as I manage to always use up the bench real estate I have.
As far as rigidity, any time you add more layers you are adding strength. There's a reason that 3/4" laminate is stronger than 3/8" or simply gluing/bolting another board or steel plate to your existing bench. I actually wish the Lee bottom plate was larger as it would further spread out the forces in play while operating the press. As it is, it definitely helps weaker bench tops against the forces applied to the edge of the bench top.
I also use an Inline Fabrication Ultra Mount for my LoadMaster. It elevates the press right up for easy observation of the stations and I can easily remove two thumb screws and swap it out and put my vice in for working on my AR or other things. While that bench has 1.5" butcher block, it still spreads the forces out even further.
The nice thing about our reloading rooms is that they are our creation and we can all have what works for us. By sharing ideas we offer other people the opportunity to see if something might work for them. Curt Vaughn gave me this idea through one of his videos and I thought it would definitely work for me and it has. For others the mileage may vary.