Back handing either spinner is super tough and not very rewarding meaning the spinners won't get enough spin to do squat other than collect the dwarves getting you closer to feast frenzy which is OK because you do need it. Spinner reward (getting to Erebor) is definently easier using left flip to right loop and vice versa.
Here's what I do. Skill shot ALWAYS roll overs. You need Smaug mb in order to collect the Arkenstone to be able to start the mini wizard modes. Use the book ramp and select an easy mode that you can beat (for instance the ring) to collect the Arkenstone. Use ring to delay 3rd lock, start another mode and start SMaug mb. Then shoot the right ramp (lock) to start Smaug mb. You'll "likely" collect 3 Arkenstones doing this. Smaug, the mode you started and feast frenzy which will start after smaug mb ends. When feast frenzy starts, focus solely on the spinners because you only have to start feast frenzy not finish it to collect the stone. Get to Erebor, collect your stone. Then put your focus on collecting the last stone by starting beast frenzy. At some point you should see your spinner loops light up green. Hit those because they'll add up to 2 balls into your next mode. It's kind of an insurance policy Once you're down to your last ball on beast frenzy, you'll have collected all 5 Arkenstones which allows you to play the mini wizard mode (into the fire being the first). Both holes (Balin/Ratagast) will be flashing orange, hit either one to start the mini wizard mode. Wash rinse and repeat.
Btw, to hit Ratagast using the right flipper.... hold your right flipper up as the ball comes down. It'll cause the ball to leave the flipper and if you time it right flipping your flipper will back hand the ball into Ratagast. Truly one of the most gratifying shots in this game. Also useful for collecting Kili