The verse tells them "do this and you will not fall." What this really means is that fall is possible and that it takes reminding oneself of Christ continually in order not to fall. In other words, you are not saved until you are saved (after you die).
I agree with "do this and you will not fall". All believers will do these things (perseverance). I think it really means that falling is hypothetically possible, and that no one should feel like he can rest on his laurels. In other words, POTS. One should do these things and be further confident for himself of the promises of assurance God also gives in other scriptures.
The real problem is that what +Peter is saying here is not exactly what +Paul was preaching in 'his' gospel. What I see in 2 Peter (a very late addition to the NT), and other later additions, is that the Church is trying to attenuate Pauline teaching.
I just see the Peter verse as coming at the same thing from another angle. I don't think it contradicts Paul in any way. If Paul can be seen as being in concert with James, then he certainly can be with Peter here.
Don't forget, Peter called Paul's epistles "Scripture." He noted the strong meat in them and the potential for abuse, but certainly didn't see Paul's words as another gospel.
2 Peter 3:16
As also in all his epistles, speaking in them of these things; in which are some things hard to be understood, which they that are unlearned and unstable wrest, as they do also the other scriptures, unto their own destruction.