some hardwares have special shadow to track p2 conents

no, that is a software feature.

Re saving dual dptrs the following is my method

push whatever else need pushing
push dpl
push dph
chg sfrx ;whatever your derivative need to change dptr
push dpl
push dph
push sfrx

do whatever

pop sfrx
pop dph
pop dpl
chg sfrx ;whatever your derivative need to change dptr
pop dph
pop dpl
pop the rest


Have fun,

Erik