Mine came with curved flippers as well. I think you should go that way. I actually wish we could get the blue boot/covers vs yellow that they have as they were meant to be blue per the original flyer.
I did at one time switch them to straight, but after fixing things, searching pinside and reading posts... I kept hearing Vid1900's voice in my head - they were meant to be curved. LOL
Now I am waiting for vid1900 to chime in.
https://pinside.com/pinball/forum/topic/for-sale-time-warp-williams-1979-1980#post-2857002
https://pinside.com/pinball/forum/topic/lets-do-the-time-warp-clubagain/page/3#post-4382830
Vid1900:
The curved flippers (they were never called banana flippers by Williams) are the only way to spin the ball and blast all 8 targets at once.
You can never do it when anyone is watching, because they would cream their jeans.
or
The regulars won't do the roundhouse spin trick where the ball knocks all the targets down in a single loop.
I like the challenge of having something different vs just another Italian Bottom game.
But it's a quick fix for whoever you sell it to to put back right.
Do you have the ROMs that fix the sound bug?
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That all being said, I don't know that I have ever hit all of them in one shot. LOL!