A lot of peoples only complaint about the fat cat is the hollow tinny sound it has. That was my complaint as well. After thinking about it I figured the baffle is recessed so far back into the canister that the exhaust hits the 4" canister walls before exiting causing that hollow sound.
So I moved my baffle back towards the exit end of the canister about 3.5".
The 1st pic shows the finished product.
The 2nd pic shows a 3X4.5 extension I added to the front of the baffle. Moving it back created a gap inside the canister and with the extension the exhaust exits the header directly into the baffle. It was a tight fit over the front of the baffle but I secured it with a small screw and nut to keep it from coming loose and rattling. The baffle on the left is an unwrapped concentric baffle.
The 3rd pic is the difference between a wrapped perforated baffle (the one I'm using) and a concentric quiet baffle.
My D&D now has a deep rumble to it and is actually quieter at cruise. NO more hollow sound. I had to drill another hole in the canister to secure the baffle. My seat of the pants shows no difference in performance.
The cost of this mod was $2.69 for the tail pipe extension I bought at O'Reilly's

 

 

I just installed the same system on my bike and was amazed at how loud it was!!! I ordered the "standard" baffle. I'm still not sure I didn't get the "loud" baffle. Do you know how to tell the difference?

I also might just try your trick.

 

Hollow tinny sound? Where do people get that? They must need to get there hearing aid adjusted.

 

I was all set to buy the D&D system till I heard about the hollow tinny sound. I had a set of V&H pipes on a Softail and hated the tinny sound. I think I'll stick with my Rineharts, so far they have the best sound IMO.

 

Well, I installed a Fat Cat on my 103" Streetglide in May. I thought the exhaust sounded hollow but only between 2500 to 3000 r.p.m. and light on the throttle. I had it tuned and I thought it sounded great when the tuner rode it around his parking lot to the back of his shop. I had a tire put on yesterday and the wrench rode my bike up the street about three block and back. It sounded great! The wrench told me "I really like your exhaust, it sounds awesome." It still sounds hollow to me when I'm riding it between 2500 and 3000 light on the throttle, but I don't think it sounds like that to other people. I'll gladly live with that because my low end torque is amazing compared to my old true duals, and I can still enjoy my stereo.

 

What he said!!!

 

I love the way mine sounds! Standard baffle.

 

I really want a set but I am very leery about the sound. I have not run into anyone locally with a set.

 

I love the sound, standard baffle is loud!