You didn't ask me but -
Slingshot Celeritas Strapless 5'8" 5lbs 12.6oz w/ 3 SS fins (epoxy?)-
Board snapped in front of front foot from rail to rail after 90 mins of light use. SS said tough luck and offered me nothing.
Only the top deck broke, including the bamboo, the bottom of the board is intact.
Dumpster Diver 5'7" 6lbs 8.8oz w/ 3 F4 fins (fiberglass) -
Buckled and delaminated under front foot. I bought this board used. It was a mistake all around. The CI construction has no chance of standing up to kiting.
SharpEye Blowfish 5'5" 6lbs 2.4oz no fins (fiberglass) -
Buckled and delaminated under front foot. This board was well used when purchased and served me well before failing.
Rusty Pirhana 5'8" 6lbs 11oz w/ 3 F4 fins (Surftech)-
Deck of the board broke through under heal of front foot. Repaired with carbon, snapped it on one rail in same location today. I bought this board used and ride it hard.
Rick Burhans Westwind 5'11" 6lbs 11.8oz w/ 3 M3 fins (fiberglass)-
Snapped under or slightly in front of front foot. I bought this board used and rode it hard.
American Surf Solutions 5'8" 6lbs 1.8oz w/ 2 M5 fins (fiberglass)-
Deck crushed both sides of stringer under front foot for a 6-9" length. Glass never cracked through though.
I also snapped the nose of a Minami 5' 10" when I pearled in 6" of water, and completely destroyed the Bobby Z 6'4" I learned on through neglect and inexperience.
Curious Was the rusty a tufflite or no?
Looking at your board selection you're primarily riding SURF surfboards. Which aren't designed for impact AT ALL.
(excluding the SS board)
Most kite surfboards are WAY more reinforced for impact but are often times heavier than sin.
As for the SS celeritas
Ive seen a lot of broken celeritas boards they rarely survive a roll in the wind or a crashing onto shore and upon inspection appear poorly reinforced, relying on a thin skin of bamboo and glass. (although I haven't seen under the front foot. there may be structural foam there)
It appears the primary failure mode for you is Heel denting causing delamination, followed by compression buckling of the unrestrained skin resulting in the failure.
I'd definitely recommend a tuffite or "sandwhich" construction. as it creates an outer beam that reduces the point load on the underlying low density foam.
From my testing a front stomp pad has significant effect on the height from which the board can take a heel first landing without denting and I would recommend this unless you absolutely hate using one...your board sizes look too small to paddle anyway.
Your riding doesn't seem crazy so a lightweight off the shelf tufflite or "sandwich" construction with a front stomp pad would likely save you killing more boards without getting into anything custom.
If you're breaking these then I would want to see some more pics of failures to decide if you needed thicker structural foam (damaged underlying eps, causing failure) , higher density structural foam, (HD foam dented causing delamination), or more glass underneath your front foot. (foam sheared) to prevent further failures. But now we're getting heavier.
Although beautiful and good at reducing point loads when combined with sandwhich construction, for weight concerns I am not a big fan of wood venirs, from my testing I can engineer significantly more bang(literaly)/gram out of s-glass and HD foam than wood but do so at a higher price. That stated I have not tested all wood types exhaustively as initial results indicated this to be a waste of time. .