On the topic of placement, if you do need a monster_generic like for animations and whatnot and need it placed in a difficult spot that gives you problems like not going where you want it or the "yellow sprites" error you can do this:
1. Take your monster_generic and place it in hammer where you need it to be in its final position.
2. Shift-copy that monster_generic and move it to a big open space and hover it above the ground. Then give it a name.
3. The in-place monster_generic that you first made, turn it into a scripted_sequence (delete the model path keyvalue) then choose the named monster_generic as the target monster. Then set "movement type" to "instantaneous".
(if you need to check "not solid" for your monster)
On map run the scripted_sequence will now take the monster_generic and place it into place with no errors. This is how "pipebubbles.mdl" in blast pit chapter and other models stuck in complex geometry are placed with no errors.