How much bowmaking experience do you have? If your still a novice id skip trying to sinew it,because if it needs retillered,then you'll more than likely take off the weight you just added and have the same poundage bow,or less. The sinew wood have to be perfectly laid out evenly and the same amount in each limb to not have to do much retillering if any,which isn't easy to do if you have never sinewed a few times.
You wood be better off adding a belly lam that's makes it 10-15 pounds heavier than you intend and retiller. But again,if you don't have any tillering experience you could still end up with the same weight bow,or worse.
Id let it be if you have never done much bowyering.