Seat hole positioning

[TheArf]

That doesn't mean that the holes will line up you get either the front pair or the rear pair but that doesn't mean that the other pair will come in line with your steel work and if it doesn't then you will either be cutting half of what you have already done to move it of adding even more steel and weight.
The only real benefit I can see in that is you are adding triangulation to the floor.
just my humble opinion.

Arfon