Powerhead Placement

Hey guys I have a 135 gallon 72” mixed reef tank and I can’t get the flow right. I can’t seem to make all my corals happy. I have LPS and SPS. I have two Neptune Wavs and just picked up 3 mp40’s that I have not installed yet. I have somewhat of a corner over flow but doesn’t go all the way to the corner, so there’s probably a foot gap between the over flow and glass of the corner. Right now I have the Neptune wavs across from each other on each side close towards the front of the glass. I’m planning to put the three mp40’s on the back glass. Is that a good idea? I know everyone’s tank is different due to the aqua scape, corals etc. I’m deciding on either putting 3 mp40’s on the back glass and Neptune’s facing eachother on each side of the left and right glass, or the two wavs on the back glass, and two mp40’s on one side of the right glass, and the one mp40 across to the other side on the left glass.

My question is 1. Is there any tricks to visually see your flow, i’ve tried sticking a plastic rod inside and kind of feel the flow. I watch watching the micro bubble test, I’m trying to figure out the best way to do that.

2. Can you post some FTS of your tank so I can get an idea of your powerhead placement.
Any advise will be helpful!

Thanks in advance