Bob Hackett
I just don`t understand this design.
As I said in a previous post that force really would have been better absorbed thru the opposite end of the screw and would be easily captured and distributed by a thrust plate and collar at that end. That plate would then distribute the force into the body of the bench which is far stronger and more capable of dealing with that force. The end cap is the wrong place to concentrate this force IMO.
If the end cap does anything more than act as a support for the handwheel end of the vise screw it`s setting yourself up for failure. That`s why those bolts are mandatory additions and since they thread into end grain ( not a recommended application) they have the appearance of being an afterthought and not even a good one at that. Perhaps that is why there seems to be an overabundance of them in the pics. Barrel bolts or a backing plate let in thru the bottom of the bench top would be a far better way to fix this design flaw.

Good thing that vise is activated by a relatively small diameter handwheel. If it had a normal size rod type handle acting as a lever I`ll bet you`d have no trouble ripping those lag bolts out of the end grain and separating the end cap from the top. All it would take in that case would be one overenthusiastic teen age football player and your bench would be toast.
I am frankly surprised that someone recommended this particular version of this vise.