Volvo Penta Thruster QL series BP-800 prop install

[Homelite]

Hello. I am installing the two props on this thruster. I am not the one that took it apart. My question is...On the two allan set screws that thread into the props, do they get screwed all the way in? I know they go into the 360 deg groove on the prop shaft, but how far do they go in? Heads flush against plastic prop hub? Or, do the heads stick out a bit? I don't want to crack the props! Secondly then, what holds them in? Thanks in advance. I searched high and low in the web for this but could not find a thing...