It is to my understanding that it is grammatically correct to say:
If I be [something], then [something].
because 'were' is the subjunctive of 'to be'. However, is it correct to use the subjunctive of other words in a similar way? For example:
If he jump, the trampoline will shake.
I request that he file these papers.
If it is correct, is it incorrect to use the simple present tense in those contexts?