Fitting a vice to the bench. Does it need all 4 bolts?

I have built a bench based on the design in Paul’s book and I am at the stage of fitting the vice.
The hole is cut and the vice fits nicely, which is a relief, but I can’t get access to put coach screws into the front holes as they are inside the front apron.

Should I just put the two back ones in as it looks like Paul has done in his book or do I need to cut out a load more from the apron. It’s not clear from the book. It seems to me that not putting those bolts in would put a lot of pressure on the back two but then again cutting more from the apron might weaken it. Also the book makes no mention of it and I can’t see it in any photos.

Any experience of this? What have other people done?