Weeeelll, I will stick my neck out here. Use what is comfortable for you. Similar questions come up with the piano and the guitar. Often, there will be a good reason to use a specific finger, and it may well be a reason that you (whoever, not just you) does not yet understand and it could limit you later on. To me, it seems that there may be specific instances where such may be the case. However, who is to say that this is one of them? If you use what is comfortable now so you can accomplish what you wanted, then at least you can keep momentum rather than stalling out. If later on you decide that you need to change your fingering, you will have good reason to do so, and therefore the motivation to follow through.
On the guitar, there is often discussion as to whether a person playing fingerstyle (rather than using a pick) shold "plant" the pinky of the picking hand on the top of the guitar. I did this for years when I was really into Leo Kottke's early music. Later on, when I needed to adapt to a more classical technique that allowed more freedom of the fingers, I decided to change away from planting my pinky. It took a few weeks of concentrated effort to be comfortable with that, but it was well worth it, and more importantly, it was definitely doable. By the way, Leo Kottke eventually changed his approach away from planting his pinky too (not because I did, since I didn't know him very well having met him only a few times). He made the change because of trouble with his hands, which brings up another point. If whatever you are doing when playing is causing you discomfort, stop and figure out another way to do it that does not hurt.
So, I would say go ahead and do what you need to after having put effort in doing it the "right" way and not succeeding. It may well be that later on, your fingers become more nimble with experience and it becomes possible, or you may find that doing it your way really is better for you. It has happened often enough that a person finds his or her own way to do something, and then does it so well that way, that other people start using that technique too.
We all have at least slightly (and often more than slightly) different body dimensions, capabilities in the use of our fingers, etc. What may be common practice among many people, may not work for us. When learning to play, we have to be aware of what physically works for us and what doesn't, and be willing to experiment to find what works for us individually. That includes our technique as well as our choice of instrument. For some, a tenor may be too big, or a soprano too small, or a certain style of fretboard (thick, thin, wide, narrow, radiused, etc.) uncomfortable. It really is largely a matter of finding what works for us in all these areas. Though there is commonly accepted technique, each person needs to give him or herself permission to deviate as needed.
Tony
, and I think there's always room for courtesy. When folks take the time to answer questions for you, it's nice to acknowledge that you got their reply....
