i have this exact problem the point to get the hinges to lock is high enough you are kinda lifting the playfield and pulling at the perfect angle. think ill try putting on another old set of rails i have laying around I'll post back if they fit.

We'll I put the newer style rails on my wh20 they fit kinda. Actually the bolt holes are correct spacing at the top and bottom, the screw holes in between are offset a slight amount so it will require drilling, but there is plenty of space around the rails in white water so it can be done easily without taking the Playfield out. Included pics to show the differences.
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You can see even though my white water pivoting metal arms were not going past the strike plate there is still a big difference in the angle.

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Here's the offset

After the install the game pops into service position just like any other williams Bally should definitely worth the extremely minimal install time if you have a spare set laying around.