Chiasmi of this kind, being for the most part 'words to live by', aren't concerned with rigid grammar or exactitude that rules out every other avenue of understanding, and by the addition of unnecessary specifications like quanta sint much of the impact of the original is, in my opinion, lost. Take for example the old saying 'waste not, want not'. More logical than this expression, and really quite what is meant (pseudo-imperative), is 'If you wish not to be in want, then don't be wasteful.' However, if you were to translate 'waste not, want not' into some such Latin as si non uis..., the nature of the original would be utterly lost.
Although I'm sure none of you is unaware of these things, it is altogether too easy to fall into the discussion of such endlessly circular minutia as the aspectual significance of two subjunctive tenses. I just really don't think that's what this person is interested in. He/she wants a translation that mirrors the original, not lays it out in 'plain Latin'.