Thanks for your honest on-going impressions and latest update -- I'd been wondering what'd happened to your MG6Pros. Unfortunately, it's much more common for happy customers to rave over their customs and post much more than those unsatisfied customers who often find it (too) hard to express how they hear things or talk about their whole customs experience; they very often, sadly, either say nothing at all, or write a single post or two at most. This is even more the case when HF'ers find they want / have to sell their custom sets and, for obvious reasons, will not tell the whole story.
Although I think it's unlikely FS will manage to improve the sonics on your MG6Pros --sorry, but I don't mean to be too pessimistic-- I do hope there really is something they can do about it.
You may remember I'm pretty sceptical when it comes to the whole issue of burn-in, though I still always give all my IEMs 5-10 hrs' burn-in, both BAs or DDs, but, I'm curious, how many hours' burn-in + actual listening time have you given your new customs? Like Isaid, it's not that I believe in any sonic changes after burn-in, but I do know some may tell you you still need X number of hours on your MG6Pros, specially since this is a DD-based IEM.
You may know this already, but I recently got myself a pair of Atrios M5 (with MG7 driver) and was very pleasantly surprised to hear the excellent SQ these deliver, and though you may also know I'm not in the market for a second set of customs, the MG6Pros would've been on top of my list along with the Westone's ES5 -- unfortunately, the Merlins, which I'd also consider, specially after getting my K3003s, would not be on that list for the simple reason that I'm not overly impressed with what I've seen happening with UM's CS in the last 5-6 months, plus the added looooooong waiting & shipping times in case of re-fits or other issues that have always been reported (in the case of my ES3X I had to have three re-fits, ie 4 sets!, much like you now, BTW, but at least Westone were always very responsive, and shipped every set within a week after they got my faulty set, but I will NOT deny that my whole customs experience was very, VERY frustrating.
Your comments on the MG6Pro's bass are really very interesting (thanks for not being a fanboy!). I wonder if, at the end of the day, getting it 'right' may ultimately be some sort of limitation of dynamic drivers, much like the limitations of BA drivers, in my view -- at least in the case of IEMs: the EX1000 is by far the best DD IEM I've heard (definitely more sophisticated than the Atrios, but the latter is very good, and a better all-rounder), though the Sonys could be merciless with poor recordings and very impressive with good recordings / (re)masters, and their mids, though quite good, ultimately could not match the ES3X's (and UM3X's) or K3003's, to these ears, that is. Having heard the Atrios & K3003s, more bass would kill my ears, or kill a lot of the music I listen to, though I have to say the AKG's bass is really in different league to that of the Atrios. BTW, I know when you spoke earlier of the MG6Pro's bass, you were not just talking about bass quantity; I wonder if the different vent options would ultimately work for me. But, like I said, I'm glad I'm not looking for a new set of customs.
Anyway, I hope that at this stage --seeing that it's no longer a fit issue-- it's something that FS can deal with and improve upon, specially after having spent over $1,000 on an IEM. Of course there's always the possibility that the MG6Pro signature is ultimately not your cup of tea.
Look forward to further updates, I really enjoyed your Merlin review and your short, but very concise UM3X review.
Best of luck!
