Thanks to both of you for your feedback.
My only concern, though, is whether it might be more awkward to do so for the long term. Though I don't know the piece, this would seem like it would be at least a relatively brisk tempo ("Allegro" though "non troppo"), and I would think it might be a bit physically straining to play one figure in the same hand, presumably from the wrist.
Strain isn't too much of an issue since the piece is quite short, and each hand only has to play two consecutive note pairs once in each cycle of 8. The hand action is similar to that which one would use in a legato context, with the right hand changing shape as it goes from 25 to 13 (or the left as it goes from 14 to 25), except that to avoid playing it too legato, I make this shape change happen while the hand is slightly off the keys, there is very little wrist action.
Whenever I do something like this I always think of that clip I saw in a nature program once. There was this greenish lizard-like creature standing on desert sand too hot to have all four feet in contact with it the whole time, so it just stood on its left forefoot and right hindfoot for a few seconds, then switched over to right forefoot and left hindfoot for a few seconds, then switched back, and so on. I just think of my hand imitating that lizard, putting all its weight alternately on 14 (or 13) and 25.
I've sometimes had the same thought for alternating passages (i.e., that it would be easier to give one hand, usually the left, the extra notes), but then when I worked it out discovered that it was a bit awkward, then gone back to practice the way it is written. The latter seems more difficult to learn originally, but then in the end results in greater fluidity.
I know exactly what you mean. Even when there are no printed fingerings, an obvious one often presents itself, then I discover an "easier" one, which helps me get further for a while, and then later I discover that the "more difficult" one is actually easier or more effective.
I agree with you on the first; play all with RH and the fingers you identified.
Thanks, but I disagree with me on this one. Playing all with RH was easier to begin with, but in virtually "no time flat" I've come round to the view that alternating is not that difficult here, sits quite well, and is more effective in avoiding playing too legato. There was a typo in my first message, by the way, the L4 should read L5: I play it (R3 L2 R5 L1 R1 L5 R3 L2), and in part what makes this easy is the 5115 symmetry, and of course the fact that every finger only ever plays the same note so need not move around except to give way to the other, since the Bb is shared by fingers R3 and L1).
In the more difficult part, for me I find it easy by using only 52 of the LH for all the LH part, thereby not getting the LH sucked deep into the keys. The pattern is simple; you'll have it in no time flat!
I hope your confidence in me is well-deserved. I may well get there in the end (it's already starting to feel possible), but I can always revert to my cheat fingering if needed.
I had this notion that alternating might have to involve some under and over, but if I understand you correctly, the LH stays underneath the RH all the time, its low profile with 52 making it easy to slide under while the RH plays its Eb Bb and G D (not sure yet whether RH should do 25 all the time as well, or whether it should do 13 for the Eb Bb).
There exists, of course, yet another cheat fingering. Noting that the upper note of each fifth interval is the same note as what was being played when it was just one note at a time, and noting that playing all of those with just the RH is sort of OK, then one could simply play all the lower notes with the LH. But then this method has the same drawbacks as which make the alternating-hands fingering preferable even for the simple case.