Hey mate, I have little issue getting a seal on the uni. It has a medium depth fit but the housings are smooth and fairly compact so they slot nicely into my ears.
They have a non-recessed 0.78mm 2-pin connector that fits my aftermarket cables just fine.
Customs are more fit dependent, mine fit a little too tight which gave me some pressure and the impression of a more congested sound. This was not a problem on the uni which sounded open and impressively spacious to me, especially impressive given that we now can say for sure that this is a single driver design. With a properly fit custom, I would assume the sound would be the same with the added benefit of a perfect seal every time and greater isolation.
I am thinking of going Uni since the hassle of getting impressions and shipping US to Poland. I amazed if this could out do my BGVP DM6 with 6 BA's a side at over 2X the price with 1BA. I have never heard anything from this company but have heard full the line Campfire Audio, 64 Audio and Empire Ears.