I think metabolism is going to play some sort of factor. On 50 mile rides I usually just use hammer gel and a bowl of sugar coated sugar bombs (cocoa crispies) before the ride. Post ride I drink a protein shake. From personal experience, it was just trial and error. I figured out how much was too much, and how little was too little. Congrats on the weight loss and falling in love with cycling, I did the same thing myself a few years ago.