Its always good to get a second opinion, and hopefully from a more authoritative figure. But, have you considered, that even when you have got that opinion, you will still end up testing it out your self, unless your a faith driven practitioner, but then you probably wouldn't be here and would have kept to the opinion of your first teacher?
So firstly, considered testing out the thoughts that I offered earlier, where is the line between concentration and insight? Do they require a portion of each other, or are they isolated from each other? So I'm asking you to think about what I said, but that can't be done without practice!
As to the figure of authority, the person who knows, well there are also a lot of problems with that too! Why? Because, if you read, Living Buddhist Masters, an Authoritive text by Jack Kornfield, you will see that there are quite a few different ways of doing vipassana! What I am saying here is you will go to one teacher and they will give you good advice, such as Sayadaw U Pandita jr. (the famous teacher who taught Ingram, who is also a genius traditional scholar) then you will go to a Thai monk such as Ajahn Kelyano (the only monk in australia allowed to ordain in the thai tradition, since that was revoked from Ajahn Brahm), and he will give you good advice too, though different because he is from a different school. Or instead of crossing schools such as in that first analogy. You will listen to advice from Michele McDonald on how to practice, who was/is a student of Sayadaw U Pandita as was/is Sayadaw U Pandita Jr. And though they are teaching the same technique, they will give you different advice on how to practice!
The problem is even though people have given you good advice, you don't have the context of knowledge/information, or experience, or both, to understand it! So this results, in you not trusting the advice, or not understanding it.
Lastly, the advice that is given in retreat, at that point or period of your practice is very different from all the other advice on how to practice vipassana, as it is pertinent to that moment/period of your practice. So we come full circle, to the early point that Katy made, listen to your teacher in retreat!
Additionally the reason a lot of the advanced practitioners don't keep answering questions for people such as you on this site is because questions lead to more questions! People like Sayadaw U Pandita Jr. usually just stop answering the questions and say practice! And when you actually understand, then they say something like now you see, this meaning that I couldn't have really answered that question until you actually understood it and see i did answer that question but you didn't understand it, so i just told you to practice! Which again comes full circle back to my earlier point, you need to trust in your experience, or the learning comes in experience.
If any of these points seem oxymoronic, ie to oppose each other, well you'll have to get a bit zen and realise one truth doesn't always cancel out the other, even if they appear to be in contradiction to each other. Such as, you have to work out whats best for you in your practice and you can't understand stuff until you've experienced it, in contrast to listen to your teachers advice in retreat.
Mind you this is one of the more difficult dilemmas in retreat, and you you can only learn this through experience.
Please read over some of the stuff I said carefully, as there may have been stuff you missed! I may not have, attained stream entry, but I have done 3 three month retreats and 2 one month retreats, with teachers. And it took me all that time to realise, I haven't been in high equanimity, and to refine my equanimity. But I have reach the sub-nana, preceding high equanimity. Which mean I've been through all the difficult territory. A peak experience is not! your center of gravity, You need to move your center of gravity up to your peak experience, that is real attainment of the insight nana. Don't get carried away with what you've experienced at you peak, what do you usually achieve every day!
Good luck again, best wishes. This are difficult things to hear but mostly true problems.
