After many quarter mile tests & adjustments, did the 1st 6 miler in sandals, at a 9 minute pace.  It was definitely longer than $1 sandals in today's dollars were meant to go.  It took no time for the toe knots to cause blisters. The toe straps constantly got looser but didn't come undone.  They took more slack from the heel straps.  The toe knots were bowlines, so they didn't come undone.  8 years of progressively more minimal shoes & being part lion aided the transition.

Much wear of the soft foam, but manely under the forefoot, as a lion foot strike is.  Leaving the C ring in place allowed the toe strap to make a tighter loop without shredding the foam.

The toe hole was a buster to align.  Too far forward & the toes run barefoot.  Too far back & the large flap of foam wants to trip.  It eventually did feel acceptable.  Then, the toe strap needs to be a lot tighter than the internet suggests.  Would just make the whole thing tighter than a shoe.