I'm just stating that there's an alternative to asking for only 5-star reviews that will likely work better. Just asking for honest reviews (and offering a discount for them) is more ethical, and the honesty will be appreciated by customers.
Except maybe if you include a line like: "were not going to ask you for a 5 star review like others do, but reviews really make it break us and we're trying to be honest. Thanks for the support"