I'm more interested in how far does the uni span .. and then what?
Nothing? Endlessness? Other uni's?
Questions that will probably never be answered by us. By definition a Universe is a self contained area of relativity, measurements beyond it would be impossible. 3 reference points being required for any measurement, if you have them, then your universe just got bigger
But philosophically... endlessness, yes, already got it, Infinity goes in, out and on and on. Use a telescope or a microscope or a clock that never stops, no Beginnings and no Ends in sight anywhere. I consider there to be 2 classes of the Infinite, 1st Class are the Non Entities, space and time, they really are not there, so infinity is their only expression, you cannot actually measure them at all, but they have a huge effect on everything they contain...The 2nd Class infinities. Entities, things that do exist and do not appear as infinite, but due to the 1st class infinities you will never be able to prove that they are not. Yes you can fit an infinite number of Universes into a 1st class infinity and still have an infinite amount of space/time to lose them all in.
Most people, due to their finite nature, have a bit of trouble with this concept, beginnings and ends are the distinctive features of a 2nd class infinity, we are able to conceptualize them as items. But we like to ignore the 1st class Infinities because they really are not there...in a very big way! Just snip those inconvenient absences off of your Big Bang theory and call them a "singularity" erm hold on whats the difference?... No I can't see one either.

One thing Ist Class infinities don't do is explode, ever. That is purely the stuff of 2nd class infinities and they do it a lot, particularly when smashed together with great force...So I am inclined towards the idea that dead Universes "mate" to create new Universes...Now that's a Big Bang Theory!

The Silence continues. The War Of Lies has no end.