Piano Forum

The RH chord tremolos in Ravel's Ondine are obviously a challenge.  

Does anyone have tips on how to play this well if one does not have naturally great piano fingers?

In my humble opinion, it's just here where the problem starts. You are talking only about fingers. That may be right because they are those who make contact with the keys and they are those who in the last term "play" the piano but you are forgetting what Horowitz and Neuhaus called "a well prepared for the defense rearguard", that is, the rest of the body, starting on the wrist and finishing in the shoulders and, sometimes, the entire back.

In this concrete case of the marvelous Ondine tremolo, I've been playing it since more that 10 years ago and this is the way I play it (of course I'm not pretending it is the only way nor it's the greatest, it's just the way it works for me   ). Your wrist at a middle height, not too high, not too much low but allways under the height of the knuckle. A very slight wrist rotation helps the fingers in their dutty (that's what I miss mentioning in your post). Avoid any stiffness of the wrist while doing this rotation. Fingers slightly active to reach precisely the keys. Release the muscles you don't use: it is, when your wrist is on the left (chord), relax pinky (5), when your wrist is at the right, relax the fingers that a split second before played the chord (thumb, 2 and 3/4). Doing a soft and "harmonious" (it is, a non abrupt) movement of your elbow can help you to relax.

And regarding the sonority and dynamics, it depends a lot on the instrument. This pieces were not intended to be played on upright pianos. The are much more playable on grands with a good double scape repetition system (Ravel owned an splendid Erard grand piano). But if you don't have one, don't be afraid, you can rehearse the movements and still be close to what is intended. When you'll play it on a grand, that will be a great pleasure. If you own a well maintained grand, good for you  

And a last advice, look for a good teacher. A forum may help you but can never substitute the live and personalized advices that an advanced teacher can do for you, from both a musical an technical point of view. The risk of injury playing advanced pieces like this without having a minimal background is too high.   (better not talking about Scarbo....)