Hmmm, yeah, its simple, but I wouldn't exactly call it deadly lol.
That's the Ticket: F+FK, FK, B+FK or F3, 3, B3. Hits mid, mid, mid (Overhead) - Off memory I think it does 4 hits.
Hits mid so they can't duck it, fast startup can be used after a blocked sweep (B+BK) or bloced axe kick (F+BK) where they can't interupt you.
If you can hit confirm this, you can cancel before the last hit into flip kick, as you stated. The combo alone does 16%, the combo with flip kick does 19%.
Alternatively let the combo complete which slightly stagers the opponent, then you can apply pressure, by a cross-over safe jump, or dash in combo.
Although you get 16% damage with this option, will get you more chip damage from the blocked cross-over jump or dash in combo and meter.
F+FK, FK, B+FK (16% and opponent in stager state), cross-over jump punched (1%), BP (2%), FP (1%), F+BP (2%). You get 16 damage + 6 chip = 22% damage + 1/3 of a bar of meter from the blocked combo. Which is better than your 19%. We could change the combo used for chipping, to alter blocked frame advantage.
Just thought I would let you know about this. Hopefully the forum will correct me, if i've errored.