Posted about this in another thread but to make it easier to search, thought I'd post its own.
Based on feedback from @drh and @Luckylindy about this mod, I decided to give it a go myself. These guys get all the credit for trying this first.
This project requires Qty 2 Clay to PVC 4" flexible couplings (Nibco) and Qty 2 4" to 3" fitting ABS or PVC closet elbows. I went with ABS because I wanted everything to be black.
If you have a Wedge, you will need to carefully shave down the Nibco a bit to get enough clearance for the fitting to seat up tight against the hull without the Wedge bracket making that an impossible task.
To shave down the Nibco, one of these makes quick work of the task. Be careful to not cut all the way through. You have to remove quite a bit of material.
Use the wide cutting/scraping blade and it's like a warm knife through butter. Hooray for Harbor Freight!
You have to cut off the 3" flanges so they're not dragging in the water. I set mine so they were about 1/4" to 1/8" above transom level. This photo was from a rough cut. I've ground down the unevenness in the final product.
When you install, if leaving your flappers on, make sure you don't push the elbows up tight to the hull. Give the flappers room to do their thing.
From a flow perspective, these add no restriction. WOT RPM and top speed tests with these on actually showed a slight increase in performance (different days, but you get the gist).
As for how they work to quiet the boat... Noise level in the boat is lowered a fair bit. At speeds around 25, it's WAY quieter. At slalom speeds, it's a fair bit quieter in the boat and the sound is less intense. BUT, behind the boat is where you notice a gigantic difference. Check out this body cam footage of with the tips and without.