My difficulty is a bit odd, but perhaps someone out there knows of a solution.
First. My ankles and knees are not like yours. The knees? Perhaps genetics, perhaps work adapted, I can kneel for hours and days without discomfort or pads for the knees. They get a bit stiff after two hours straight of paddling on my knees, but at nearing 70, I should expect anything else?
My ankles are another story. Whether I am a genetic advancement or a Neanderthal throwback (I suspect this.) I have an extra bone behind my ankle, this limits motion, while it is beneficial in allowing a very stable ankle. I cannot point my toes. When I ‘point’ my toes, the foot will make it to about 40 or 45 degrees. It is physically impossible for me to lay the top of my foot on the bottom of the canoe when kneeling. And yet, that is exactly where my butt lands, and my weight. (Both are of numbers high enough to cause me embarrassment.)
The normal stuff sitting and paddling, my seat was installed an inch or two lower than design for that boat, tractor seat, I can paddle 6 to 8 hours, no problem. But when I slide forward onto my knees for rapids, where my skirt is also positioned, 20, 30 minutes, my ankles are screaming at me. Or the empty aluminum rental canoe, I am kneeling between the yoke and the rear thwart, sometimes getting a little butt support from that rear thwart behind me.
I have had limited success with rolling up the spare PFD and tucking it transverse under the ankles. It does help. But anything fixed there would forbid the shift from seat to knees coming into the rapids, or shifting back to the seat in the pool below.
Saddles are out, they limit lateral movement in the rapids.
Looking for suggestions. Outside the ‘box’. Knees don’t need a pad of any sort. (as long as I have cleaned the sand out) But ankles don’t bend, so they need some sort of support, (so my dainty size 15 feet can dangle a bit)