The question about "in case" and tense

Hello, everyone. I learned from my grammar book that we often use present tense to refer to future in "in case-clause". Like:

I always take an umbrella in case it rains.

I've bought a chicken in case your mother stays to lunch.

In those cases, I found that all the verbs in main clauses are tenses refer to "present". But what if they are "past tense"? I saw several examples in my grammar books:

1. I wrote down her address in case I should forget it. (What change should I make with the "forget" if I don't use "should" in this example?)

2. We took our swimming suits in case we should find a pool. (What change should I make with the "find" if I don't use "should" in this example?)

3. He left early in case he should miss the last train. (What change should I make with the "miss" if I don't use "should" in this example?)

4. In case the wall should collapse, they evacuated the building. (What change should I make with the "evacuate" if I don't use "should" in this example?)

I think, for those cases, we should use "past tense" in those cases even though the main clause has a past verb. Because I saw this sentences in another book:

5. Doctors and nerses remained above ground while police patrolled the streets in case anyone tried to leave the shelters too soon.(I think the "tried" can be replaced by "should try", am I right?)

Please tell me if I can use present tense in those occations. Thank you very much.