GM,
I've used them on all of my Excalibur recurve crossbows. Never tried two packs (6) on each side. That's probably overkill in my opinion.
They claim minimal speed loss. I can't say for certain if that's true or not as I have never chronographed any of my crossbows.
I do believe they help with noise and vibration, and I like them much better than the Excalibur supplied ones.

 

I agree with @Inspector98 , 12 might be a bit too much. Slowing the bow down. Dr Stirrup makes good products. I have used them on Excalibur crossbows to help cut down on noise.

 

I have a Wraith 430 cb, which silencer compliments that crossbow?

 

With any limb dampener (silencer) the closer they are mounted to the riser, the less loss in speed.
One can check this out when shooting the same arrow point combination weight through a digital
chronograph and moving the dampener to different areas along the limb.
Wishing you all the best.
Take care.

 

Six well-placed silencers are probably enough for a good result. Twelve could be overkill and harm overall performance. If you really want to test, do it carefully and compare the results.

snaptube vidmate​

 

I have two on each limb. Works well. I also like his DbKillers