Tuttle box is too narrow , made for wind surfers
Don't know anyone using probox ?
I think I'm gonna use KF box for the sup mast
If your using a KF box, I would recommend using 2 screws (or more) to pull the mast (strut) in. I was surprised how quickly I wore a single screw mast (Ketos) so it started to rock back and forward. Had to repot the mast head..now fine again. Probably my fault for not getting it meticulously clean on every assembly but that can be a bit difficult on a windy beach.
The original windsurfing Tuttle fin box was modified and deepened to become the "deep Tuttle" when windusrdfers started using very long fins and applied enormous sideways pressure on them. Kiteboard hydrofoiling is different and the pressure on the box is mostly straight down the mast.
Both the regular Tuttle box and the KF box are not deep and are widely used with hydrofoil kiteboards without problem. Around here there are plenty of regular Tuttle mounted hydrofoils (like my own Taaroa Joy) and we have no issues.
Be reminded that your mast is perhaps 15mm thick and so you don't really need a box that is 77mm high to take the same sideways force. (This may be oversimplifying but hopefully you get the idea.)
Also note that the mast/fuselage connection on many hydrofoils is very minimal and yet it takes much of the same sideways force.