Visit your local wake board cable park and note the heel straps.
Lou was a user for MANY years and we learned from him a better way of fixing.
Turn mountain bike inner tube inside out, clean with alcohol.
tape reinforced duck tape a few layers, flush with end,
do the same for the outside.
melt well centered hole with heated awl.
Finding best length is trial and error.
Biggest benefit is that one can choose to not use by stretching over strap.
I found finding good grip sole booties,great grip pads, and adding grip to underside of straps and heel straps made for near perfect grip but still allow
bail out if wanted!
Lou on his speed runs MANY years ago always used them and if one searches kite beach history you will see them!
Success leaves clues....