While getting all my parts and electronics together for my K4 assembly, I thought I'd post some info regarding sound bard compatibility.
Inner Diameter of K4 is 0.87" comfortably, and 0.88" tight squeeze..
Measured this against the Prizm, the CF8, and the NBv3.. Only NBv3 will fit without modification. Prizm and CF8 are about 2mm too wide for the ID of the K4 (0.93" vs 0.87"). The downer to this is that NBv3 does not support an auxiliary switch. Any one know of any way around this? I saw a post in a separate thread of someone using a Crystal Shard 2.0 with the K4 with an aux switch wired, however I know those Crystal Shards are not easily attainable.
Hope this info helps some peeps