Agree with the AB6 being a safer bet, I've redrilled areas of AB15 and AB8, seed cost is scary and most of the chances of good establishment are out of your control.
I think with the AB15 I could redrill it several times and be no better off.
Out of interest, what sort of cost/ha are you finding for the seeds?
Listening in on all this makes me so very VERY glad that STW accepted my application for an expansion of STEPS. The Bumblebird type mix is supposedly a Spring sown option, but for my heavy land, whack it in mid/late September with Aitchison is so much better...
Spring sown seed is pretty reasonable on cost from Kevin here @67/ha.
Inspection is sensible, and if a real attempt has been made and the crop struggled, then not a big issue, redrill or patch.
It is what ELMS should aspire to....!