I think the problem with Lats on the 4th line is the other winger. I mean, Bégin has some offensive talent but Muray and Downey (did you see this 3 on 2 he screwed yesterday...)
I think a Perez-Johnson-Lats is a solution. The other would be calling up Kost and do a 4th line like this :
Kost-Bégin-Lats.
Because Downey and Murray are not that usful to the team and this line would give the team 4 good offensive lines and energy (with Bégin and Latendresse)