Chizer & Bunoi 67 gallon

Greg - I edit that part out. I realized I wasn't using an aquarium calculator. duh!

Skimmin - Thanks for the kind comments. I was able to leave the return pump fully open.

Steve - Your method worked very well. It sure is time consuming and cutting a 1/4" of PVC off on the mitre off is scarry. The rebound and kick back sure is dangerous.

Brett - I have my emergency drain sitting high in the sump so the thin drain doesn't work. I did this on purpose so that I could whether something was wrong with the primary.
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Thank you everyone. I ended up cutting the primary 1" and the emergency is now sitting 1/4" under the weir itself. No crashing noises or vortex happening. The emergency also works flawlessly.

I stuck a piece of 1" gym memory foam under the return pump which helped some what dampen the noise, but you can still hear a hum/vibration. I'm thinking maybe it's the vinyl tubing from the pump to the hard pvc? Or maybe I am hearing the echoing inside the stand itself?