Drum Kit Groove Notation Using Voices

I know this is an old thread, but as my question is related to this subject, I am posting here.
I have a problem with drumset notation.
In one bar only, the snare drum has to play a prolonged halfnote tremolo with the kickdrum to help it start on the first beat. But when I try to change the stem direction for the snare drum, the kickdrum follows. I need to seperate these 2 drums, because the kickdrum also plays tremolo in the playback and it sounds awful. Using Dorico Pro 3,5.
Skærmbillede 2022-08-24 115157