I and so many others have already been where you are. I'll give you my experience only, to do with what you want.
MML - I tried the brown dog in poly and rubber. Both transferred more engine vibes than a factory mount with a 1" spacer. That is the best set up by far for a driver.
I do not think the Savvy UA is the problem exactly. It's pretty much any TT or belly pan that is thicker and more solid than factory. I've been through several and they just plain ol transmit more engine vibes. I'd bet the UCF skid gives you no relief. It's going to amplify everything too.
Any combination of TT and CV rear shaft is going to give you more driveline vibes. Some more than others depending on many things.
After regearing, I have always had driveline vibes. The only thing that has ever stopped it is a front hub kit to keep the front d/s from spinning.
I know some folks are going to argue but these are my own personal experiences. I've been through a few TJs and one highly built LJ.
I have fought with driveline and engine vibes for years and years....fretting over every bushing, mount, driveline angle, driveshaft angle, gear setup, etc. And taking advice and calling other experts such as mrblaine, and in the end I have found that I've had to live with some of it, and got rid of most of it, but some of it is just going to exist because of what it is. The transfer case design, front axle design, SWB, short driveshaft, solid belly pan on a solid frame....blah blah blah.
Prepare to remove the front d/s or invest in a hub kit. Swap out the motor mounts.
Now with you having an unlimited on such a small lift I am surprised you are having a such a difficult time. Your cat back isn't helping anything noise related either. Good luck.
On my current TJ Rubicon I only went with a 2.5" lift and am using the original rear shaft and stock 4.10 gears. No vibes at all. I know if I were to start messing with it what will happen, so it stays as is.
"The Wicked Flee When No Man Pursueth, But The Righteous Are Bold As A Lion."
'03 TJ Rubicon Tomb Raider Edition, Zone 2.5" lift, 33/12.50-15 Mickey Thompson MTZs, Warn Zeon 10S winch