As you can see from the picture above I have an mp40w on the right side of my 40 breeder. Lately I have been thinking of using two mp10s on either side of the tank for more random flow. I'm worried of tHe mp10 being too close to corals on the left side though.
The mp10's are much smaller than the 40's I have a 20 and a 10 on my 65. and the 20 is same size as the 40. If switching to 2 10's dont put em on oppostie walls I have my 20 on the right wall as you look at tthe tank and the 10 on the back wall on same end as the 20. Just food for thought if you switch to two.