Originally Posted by Trollheart

Not to be pedantic, but no, I don't think there's ever a usage of "should had". Would you say "Hitler turned towards Kiev when he should had gone on to Moscow?" No, you'd say "he should have". So no matter the tense of the sentence, I think it's "should have" always.

Originally Posted by J.R.R. Tolkien

There is only one bright spot and that is the growing habit of disgruntled men of dynamiting factories and power-stations; I hope that, encouraged now as ‘patriotism’, may remain a habit! But it won’t do any good, if it is not universal.