Researching work benches will often show many examples of the sliding deadman. I opted not to put one on my bench because I valued drawer space more.
On the rare occasion when I need to support a piece from the bottom I'll just use a clamp in expansion mode.
Well I'm glad someone uses clamps in expansion mode. I never have.
Is your benchtop a benchtop on top of a benchtop?
Also, excellent job on the seat carve. How did you do it? I've gone at mine with a grinder and a palm sander and... it's difficult to get good results.
I use an inshave (aka scorp), compass plane, curved scrapers, and sandpaper for my seats. It's laborious! Just started on another tonight and of course it has a few stubborn spots.
Good question about the bench. It's a 5" pine top but it dried funny, curving inward at the top. So I inlaid a maple strip to get the front back to square.
I find those squeeze clamps are such that when turned around in spread mode, the minimum clearance is like 6 or 8 inches because the jaws are so bulky, and they nearly never fit in where I need to, say, force a very tight mortise and tenoned frame apart.