Hi Volley,
I used Duelund silver bypass caps in my current reference speaker crossovers, attempting to bypass Clarity MR caps. I can honestly say it did nothing detectable. Maybe due to the size, about 0.047uF around a 4.7uF cap.
On the other hand, another cap I have, around 8 uF, bypassed with an 0.1uF Audyn True Copper cap was an outstanding imropovement. I tried it on the other cap too but found it changed the timber too much.
If I had the money I would love to try the Jupiter copper foil caps, cheapest from SonicCraft, but ouch.
Best,
Erik