For me the spindle length is something I do by experimentation (really), plus once the chainset is installed you can look to see that the chain line looks good. That said I think 107 sounds about right for a single ring up front.
although Shimano Cranksets are made for JIS tapers an ISO taper BB will likely still work and the crank slide in a mm or so further each side (in theory offering better support of the aluminuim IMO) this can offer smaller/shorter Q- factor which is great as long as 1)your chainline still works
2)the inside ends of the cranks do not hit the either chainstay
3)the inside ring (or spider in your case) still clears the DS chainstay