I disagree with the 4th finger on the D-flat, and I think it misses the point of this etude, which is not a fingering etude, or an etude in the style of op.10 no.2. Don't give in to the mania to "connect" everything, because this is precisely music which is not connected by fingering, but rather by the upper musculature.
In this etude you are essentially playing hand positions that you reach by subtle movements of the upper action: shoulder, upper arm, and elbow. Each of these positions also has a natural rotation, which comes from the hand/lower arm.
Looking at it this way, the grouping A-flat , D-flat, A-flat (the second triplet) with the fingering 4-1-5 is extremely uncomfortable, weak, and insecure. Furthermore, the grouping A-flat, C, C, D-flat (the first triplet plus the next note) with the fingering 3/2 - 1 - 5 - 4 is also painful.
For a successful run at this, you need to have the upper action mobile (Medtner described Rachmaninov's technique as "shaking the notes out of his sleeve"), the hand rotating, and a light second finger, or more precisely, easy action between the second finger and thumb, because it is the second finger which is used the most.
Walter Ramsey