So I was looking through his posts here and on the 7th and 8th pics it looked to me like he had photoshopped the heel area of his Vics (put a weird tan colored patch over them). I wondered what that could be hiding. But on the 6th slide you see a closeup of the spike and it's definitely had an interesting custom modification. Basically the entire heel has been cut out (including the stupid hole that Nike seems is good even though it creates a circle with a nice sharp edge right up the heel) and a skin colored elastic material has just been stitched/bonded in there. So much for needing a built up heel cup with counter etc etc (you don't). So he basically has just an elastic band heel cup in his spikes.
A little bit geeky, but it's interesting. Says to me that his achilles issues are definitely lower high than higher on the leg - so it's possibly some Haglunds'esque deal which is why he wants to remove any chance of causing inflammation there with his footwear. The alphaflys he is wearing are a knitted upper that have basically no heel counter/nothing stiff there anyway. If it was the more classic "inflamed sheath" achilles annoyance then he wouldn't have needed to modify those spikes.
Start lists still haven't come out for the 14th, so fingers crossed he has/will officially declare for the 1500.