Hi, Satra-

I don't think the purpose of the defining a sform=5 code is to say about a dataset, "please don't hold me to anything in particular".

Let's say we have a dataset aligned to the standard D99 macaque template. What sform should it have?

At the moment, sform=1 is specific-- such a dset is in original space coordinates (so doesn't apply to our dset, since it *has* been aligned to something); sform=3,4 are specific-- such a dset has been aligned to Talairach or MNI standard space coordinates, respectively (so neither applies to our dset, because our standard space is not Talairach or MNI). Then, sform=0 is uninformative -- such a dset has an "arbitrary" or "unknown" coordinate space (doesn't apply to ours-- we *know* it has been aligned, and we know to what space). Currently, then, our "best" choice might be whittled down to sform=2, *but* this is ambiguous as to whether the alignment was to "just" a subject's anatomical or to a template-- and, again, this is a poor option for us because we *know* it has been aligned to *a* standard space (just not one in the very limited set of Talairach or MNI).

Therefore, instead of losing important information, we would like to use sform=5 to resolve this ambiguity for our case (and what will surely be a growing number of simialr ones)-- by introducing it to describe a dset that has been aligned *to* a standard space (that isn't Talairach or MNI).

One other option would be to introduce a new integer for every new template space, but that would get unwieldy and lead to constant updates. Hence our present suggestion.

And to be clear, we are not proposing to change the meaning of sform=2; it is just that that value is a bit unfortunate in its non-specificity/ambiguity.