Well, first off, I think Madelyn Sophia Stafford (or something similar) would totally work. I find it charming! But for another middle name, here's some options you may like:
In my opinion, since you already have sooo many syllables, a one syllable second middle is best.
Madelyn Sophia Faith Stafford
Madelyn Sophia Jade Stafford
Madelyn Sophia Blue Stafford
Madelyn Sophia Paige Stafford
Madelyn Sophia Firth Stafford
Madelyn Sophia Leith Stafford
Madelyn Sophia Fern Stafford
Madelyn Sophia Pearl Stafford
Madelyn Sophia Blair Stafford
Madelyn Sophia Wren Stafford
Madelyn Sophia Lane Stafford
Madelyn Sophia Kay Stafford
Madelyn Sophia True Stafford
Madelyn Sophia Lark Stafford
Madelyn Sophia Poe Stafford
Madelyn Sophia Blythe Stafford
Madelyn Sophia Rain Stafford
Madelyn Sophia Maeve Stafford
Madelyn Sophia Lake Stafford
Madelyn Sophia Dawn Stafford
Madelyn Sophia Gwen Stafford
Madelyn Sophia Fleur Stafford
Madelyn Sophia Ruth Stafford
Madelyn Sophia Reese Stafford
Madelyn Sophia June Stafford