Rip explains, here:
The Starting Strength Bench | Equipment
I sat on one when I was at WFAC last month for a SS Seminar, but I did not it use to bench press. Some poeple thereshad tried it, and liked it.
10 inch Bench Width
1) Yes, it works well for a small person
2) No, it doesn't work well for a larger person.
There is no, "One Size Fits All".
"The big guy does not depend on the width of the extra 2 inches for stability." (12 in vs 10 in width)...per Mark.
Actually, the wider the bench (even 2 inches wider) the greater the stability; for large lifters and even more so for smaller lifters.
Joe DiMarco
DiMarco along with George Frenn invented the basic Louie Simmons' Westside Training Method, circa 1970.
On a side note, "Original Westside Squat Training Method" is uniquely different in comparison to to Simmons Method. Each provide a slightly different training effect.
DeMarco also invented the "Lever Action" Powerlifing Belt.
DiMarco is one of the best Strength Coaches and inventors that virtually no one has heard of. I was initially clueless. He was decades ahead of his time.
Another novel item that DiMarco invented is the...
Broad Back Width Padded Bench Press Training
It is a Wide (about 16 inches) Padded Board that is placed on a Bench Press.
The additional width provide more stability to the Bench Press, allowing you to overload the movement with more weight.
While living out in California, I trained with DiMarco a couple of time and used the Wide Padded Bench Press Board.
DiMarco's Wide Back Bench Press Board is somewhat like...
Floor Presses
Floor Press provide greater stability; using more weight to overload the Bench Press.
Sliding On The Bench
The Bench is slick. There is going be some unstable sliding on it.
That is specifically true if you preform a Powerlifing Bench Press; using Leg Drive when you Bench.
In all fairness, you will get some sliding on some Padded Bench Presses. Some sliding occurs on my Padded Bench Press.
The remedy is...
Kitchen Shelf Liner
If you slide on your Bench, any Bench, purchase some Kitchen Shelf Liner; also used under throw rugs to keep them from sliding. It is around $10.00 at Walmart in the Kitchen Section. You can also find it at Lows and Home Depot.
Cut it to fit your Bench and lay down. You stick to the Bench like "Fly Paper".
Now that we've looked at the downside to a Narrow Bench let look at...
The Benefit of A Narrow Bench
A Narrow Bench allows you to drop down into a fuller range movement, especially with Dumbbells. This allows you to more completely work the muscle involved through a greater stretch.
Bench Width Training
A Narrow Width Bench provide a different training effect from a Wide Back Bench.
Your Training Objective dictates your choice of Narrow or Wide Bench; providing you have those options.
Kenny Croxdale