Thumb slipping - valid resource?

[stormx]

Hi !!

Another fingering question 
I am learning Chopin waltz in A minor, Op. Posth.

In the second section, i have to play, with RH, a G# with finger 1, followed by A inmediately above. I can play A with finger 2, between the blacks keys. However, i have tried letting the thumb just SLIP from G# to A, and it seems confortable (the passage is marked legato). However, it seems a weird method 

Question:
Is this slipping method acceptable?
I do not want to adopt weird fingerings, or bad practices. What do you think?

PD: if you are familar with the piece, and you can suggest the fingering for those bars, i will be very grateful. My score has very few fingerings 

[quantum]

can you please post a bar number?

[stormx]

can you please post a bar number?

Sure.
Bars 37-38-39-40 (without counting repetitions). RIGHT HAND
Righ hand G# in bar 39 should be played with finger 1, i beleive. "A" is first note of bar 40.

If anybody can suggest a complete fingering for this bars, it would be great. I am omiting ornaments at the moment, but i want to work on a fingering that would not have to be completely changed later (when adding the ornaments).

Currently, i am doing:
Bar 37: B(1)-C#(2)-D(1)-F#(4)-E(3)-D(1)
Bar 38: C#(2)-B(1)-C#(5)-G#(3)-A(4)-F#(2)
Bar 39: E(1) (changed to 3 with the mordent with F#(4))-D(2)-G#(1)-F#(4)-E(3)-G#(1)
Bar 40: A(2) (A(1) ?)

As you see, i play one mordent to change fingers.

Thanks for your help

[faulty_damper]

Question:
Is this slipping method acceptable?
I do not want to adopt weird fingerings, or bad practices. What do you think?

This method is acceptable, though the use of the pedal could be used to sustain the tone so it does not have to "slip".  This technique is highly effective to achieve legato in dry textures, like contrapuntal ones, especially in fugues.

Don't limit yourself by what you think is incorrect - if everyone did so, you wouldn't be playing any piece by Chopin because according to his contemporaries, and himself at one point, his technique was horrendous and he was embarrassed for it because it did not fit the norms of the time, id est, "classical" technique.

[bernhard]

Best wishes,
Bernhard.

[whynot]

Well, the above fingering clearly solves this problem.  I want to respond more in general to whether it is actually okay to do the thumb thing.  I am into cooking and was reading some article by one of the great chefs about grilling beef.  He said that, to test it, cut into it in a hidden place with a very thin knife.  He went on to say that of course the readers would be shocked by that, that great cooks are supposed to "know" the perfect moment, and shouldn't have to "resort" to this.  But that this was actually something that all the "big guns" did, only no one admitted to it.  He said, basically, just don't get caught.  That's pretty much how I feel about the thumb slide.  I hardly ever do it, because there's usually an elegant way to solve those problems.  But once in a while... you just have to play your way out of a situation however you can, and if you can make it sound good and not get caught, well....  just my thoughts. 

[tumababa]

I would agree with that.  There's got to be at least a few situations in the millions of pages of piano music that exist where a thumb slip is the way to go.  I'd probably hide it from my teacher though, if only to avoid a lecture on fingering.