So I'm confused. Are you sitting for the April or August exam?
My feeling is that you want to be in a good position so that you WON'T have to retake and retake until you get the score you want. Knock it out the first time. Retaking never looks good, especially if you're not bringing up your score. If you feel that putting it off will put you in a position to do even better, then do so. If your scores are inconsistent or you have a particularly weak area, work with it until it's on the same level as the other sections. Fight like hell until the 11th, and if it's still not where you want it to be, then send in your refund form, and work at a pace that can adequately prepare you for August. Else, fight like hell till the 22nd, and slay that b*tch.