Deeper ancestry?

Health warning:
This post contains DNA terms - check the ISOGG Wiki glossary  for further explanation of the teminology, and my amateur interpretations of results - I welcome further explanations, suggestions from those more knowledgeable.
 
As those following the FAIRBAIRN Surname DNA project already know, the majority of the FAIRBAIRNs tested to date match, and belong to haplogroup I1
This grouping indicates our deeper ancestry, ie pre-surnames, 1000s of years ago, instead of the  genealogical timeframes covered by our charts, and the results shown on the DNA results page.
(The haplogroup link above takes you to WikiPedia, which explains I1 diverged from I about 15,000 years ago).

A 2013 (and rapidly evolving) haplogroup tree for I exists on the ISOGG pages.
All we know currently about our matching I1 participants is that we are all still in the generic top level bar one of I1, terminal SNP of M253.
Two of our particpants have determined that we are "L22-, M21-, M227-, M253+, M72-, P109-, P259-", which I interpret as ruling out subclades of I1a1 and I1a2.

One participant has also joined the I1 yDNA Haplogroup project to see what else we may learn.
Results from thousands of tests may be seen here.
I had hopes that we may, eventually, find how far back the common ancestor was for the FAIRBAIRNs and our matching ELLIOTs.
As yet however, there isn't much in the way of timescales associated with the deeper haplogroup tree, so that is probably a rather vain hope, particularly as we only have STR results in the main, and only the above indication of where we don't fit on the tree.

The participant who has joined the I1-yDNA project has been placed in the (very large) sub category of  "I1 generic (I1-AS (generic)) consider ordering Z58, Z63 & DF29"
which SNPs would determine whether the subclades were I1a3, I1a4 or generic I1a respectively.
Only a very small step towards a potential goal of when the ancestry diverged for the FAIRBAIRN/ELLIOTs.
Should one each of say the ELLIOT and FAIRBAIRNs nearer the modal by STR results be willing to upgrade for the advanced tests for the above three individual SNPs, please do contact me (see footer of most project pages). There is no point in more than one or two participants upgrading as results at this level should be very similar, if not identical - each individual SNP test appears to cost $US29.

I had considered suggesting a Geno 2.0 test for this aspect, transferring results to Family Tree DNA, but there appear to be problems with Z58 (and Z62) in the Geno 2.0 chip, and the transfer of results has not yet been fully ironed out. So more cost effective and reliable to simply test for additional SNPs as and when desired/indicated should anyone be curious about our deeper ancestry.