Oh yeah. If the fit is even a tiny bit off, it can be really annoying. You can keep feeding that anxiety until the blood pressure makes your temple veins explode. 
Oh yeah. If the fit is even a tiny bit off, it can be really annoying. You can keep feeding that anxiety until the blood pressure makes your temple veins explode. 

Well, I finally got to audition the 4.Ai and 3.Ai on a meet this Saturday.
Unfortunately, what could have been a more-or-less in-depth review was spoiled by a bad fit, so I'll just give a basic set of impressions.
First of all, here is the problem I had. The 4.Ai and 3.Ai have a pretty wide nozzle which mimics the design of customs in how it widens until it meets the body of the IEM. It is designed that way to fit snugly into your ear canal and create some nice isolation in the process, but in my case, this made it impossible to fit into my ear. Even with small tips, it wouldn't fit as deep as it was designed to. This resulted in two things: a shallow soundstage and sub-par isolation.
On this pic I am using the medium red tips with the 4.Ai. You can see how they hang out of my ear slightly. I have also used smaller tips. This isn't due to the tips but because of the nozzle shape. People with small ears, beware!
But let's move on to happier matters. Here are a few 4.Ai impressions. 
Impression #1. They're tiny! Probably one of the smallest universals out there in this price range. I'd say they're about 2 centimeters in length.
Impression #2. They have more bass than I thought they would. This is subjective, but I almost found myself wanting less bass. I suspect that my fit problems contributed to this (I didn't have any problems with seal). Nevertheless, they extend quite well, in both directions.
Impression #3. As much as I could judge sound signature with the fit problems, they seemed to be pretty neutral with a little bass boost and maybe ever so slightly recessed in the upper midrange. This varied greatly with tips.
As a result of the fit problems, I will probably get the 4.A CIEM, but only if Heir Audio has some sort of refit policy, since I'm a young and growing person (I'm looking at you, FullCircle
).
EDIT: That's kind of odd, I could've sworn I wrote this in the 4.Ai thread. What a silly mistake. Hopefully a mod can move this post.
This is a good take and what I would expect them to sound like though a bit extra bass will sound more correct when on the go and bass is masked by ambient noise. It's a good description of a twfk plus woofer done well.
There was a post with specualtion as to why the 4.a and 4.ai sound different with the same bits. It won't just be the tips and fit. The customs will also have longer tubes of which the contained air mass will add some small resistance. TWFK may work better in that config.
Do you think the A4i is a better purchase than the W4's?
Was. It's back for me.
And their website is down...again. How the heck do you order these things? lol
Does anyone have an email address or phone number?
Fast. Very fast.
Sure. It's on their webs... Oh.
I don't know about 4.Ai but 3.Ai is not my type.
Perhaps you prefer blondes? They have more fun.
I've been away for a couple weeks. I'm surprised not to see a little more action on this thread. IJokerI get these yet? Doesn't look like it.
IJokerI removed himself from the tour.
I updated the first post.

I've got four pairs of customs (including custom earplugs and custom sleeves) and my left side is always a problem, even with three different ear impressions made by three different people. So yes, it happens, and yes, you must work with Heir and have the problem solved, for if there's a bump, then seal and comfort will both suffer.
Note that, like you, I believed the extremity of the tip hit the bone; but in my case, I discovered it was the bend of the tip, not its extremity: It squeezed the place where the skin first meets the bone.

IJokerI removed himself from the tour.
I updated the first post.
I've got four pairs of customs (including custom earplugs and custom sleeves) and my left side is always a problem, even with three different ear impressions made by three different people. So yes, it happens, and yes, you must work with Heir and have the problem solved, for if there's a bump, then seal and comfort will both suffer.
Note that, like you, I believed the extremity of the tip hit the bone; but in my case, I discovered it was the bend of the tip, not its extremity: It squeezed the place where the skin first meets the bone.
I have to say that I was looking forward to seeing what Joker said about these two :(