How long of rest are you doing between planche attempts?
What is your dip strength like? Good if you can do 4 ring HSPU I'd imagine.
Personally, I would spot the tuck planche with a swiss ball or box to get that feeling in it of leaning more. This isn't really a workset but a drill to understand how to lean.
We've talked about it and I apologize that I can't remember, but how long can you hold your L-sit and other feats of abdominal strength and lower back strength?
Planche work isn't just about upper body strength.