I've seen a few language forums and blogs where the matter is discussed (eg. "If I would.... then I...").
As much as it could be argued as possible (both are technically past tenses of will/may), the general advice is DON'T ever do it. You would then need to defend your reasoning for doing so, and even then your justification may not be considered acceptable. It's better to write a clear sentence for your reader than expect a technicality to do your reasoning for you.