Advanced Tuck Planche help

I have this problem,i can hold the tuck planche for 60 seconds with good form and i can do 5 tuck planche pushups with hands on books,but when i try the advanced tuck planche it just doesnt work,i can't straighten my back.Could this be insufficient lower back strenght?I have been doing the weighted pike stretch,rll and other lower back exercises for months.

At what progression are you at with the other lower back exercises?

I can do the pike stretch with 15 kg holding it on my neck(with something soft on it) and i can do a straddle press to handstand.

try handstand lower down with adv tuck planche

straddle press on floor right, not wall?

I think you may just need to practice the advanced tuck planche more to learn that position. you can do the advanced tuck front lever or back lever, right? if you can and you know that position, it's merely a matter of practising that type of planche more because of it's learning curve.

can you do it slightly higher than parallel around 30 degrees above horizontal? if it's merely that you can only hold 1-2s you just need to practice it more, imo.