I do not have any eGo batts, so I tried the T-atties using my 280maH 510 batts to test it using lower voltage. The ones I have are around 3.4V and I can confirm that anything lower than 3.7V doesn't quite give me a satisfying vape.
I remember how I used to hate vaping using regular 510 atties on those batteries. Instead I used to use KR batts.
I didn't face these problems using my normal Riva batts. If I leave the tank atties half screwed on the Riva SE batts, they wobble much less.
I cannot check for myself due to not having an eGo batt, but I read somewhere on this forum that the draw on the Riva batts is a bit tighter than on an eGo. I noticed that the draw is even tighter using a Riva SE batt.
As a side note, what I sure noticed is that the draw using a regular 510 XL batt is that airflow, hence the draw, is much better, but that is because there's not the old (and now useless to me, since I only use tank atties) threading for the optional cone that was used with the normal 510 atties.