Well I used 20% tpa lemon (the water soluable one), 3% koolada, and 2% EM and its pretty good. Could be more lemony but Ive yet to make a batch with some sour (or malic acid) added.
I use Flavor West's Lemonade flavoring and add sweetner (sucralose/ethyl maltol per preference) and LorAnn's Tart and Sour to taste. Makes a great Lemonade that you can tailor the sour/sweet to your personal preference fairly easily. 15% on the Lemonade flavor itself is a good base to add the sweet/sour to.
Hope that helps somewhat. OSDIYS has the necessary items.
^^^^ That sounds pretty good