Inspired by a few things:

a) switching to a Concept2 rower/erg (one of my sons is getting into rowing), I found that barefoot or sock only rowing is a bit painful on my heel due to the hard plastic heel catch (I think made for shoes)

b) my stiff back and desire to not have to put shoes on every time I want to row

c) a guy named Paul Smith on the internet who made a nylon strap solution http://www.ps-sport.net/SwingSling.htm

I literally just got PLU and did a calibration test print, and was in love with the material (having only printed PLA up to this point). So a 3d print it is!

This is a bit niche, and likely won't get a ton of downloads - but this is so nice, I have to share :)

I could have made the heel loop a little bigger, but I want to use it for a month and see how it breaks down or stretches. The loop that attaches to the flexifoot is tight but that is so that it is consistent - just stetch and slide it on.