Whilst I thank you for those kind words, perhaps my original post was rather unclear - I've now edited it!
Regarding the 'surplus capacity' - imagine that you are a road transport company director. "We want a new truck which will carry at least 70 bananas of stuff", you decide. So you go to the purchasing department and say "Get some tenders for our new truck". Eventually 2 are accepted for assessment - 1 can carry 75 bananas worth (or, if you want, the firm will modify it to carry about 90). It will fit your garage and will get throught the company's yard gates. But the other can carry 111 bananas worth (over 50% more than you decided that you needed), although it has a wacky new transmission system which none of your employees has ever come across before, it won't fit in the garage and it won't get through the yard gates.
Which would you want to buy.......??