Chai,
Here's the info on the BDR "pucks"
The "pucks" have a predrilled hole on both sises (1/4 X 20). The "puck pit" has one predrilled hole and an indent (pit) for the tip of a spike or cone.
Two sizes I would recommend.
1) Jumbo. 3-1/2" diameter / 1-1/2" high.
2) 2-3/4" diameter / 3/4" high. That's what I have.
Then there's the Mark III or Mark IV designation.
One is supposed to be voiced to be a bit "softer" on the sound. I have no idea what that's about except if you have a "bright" sounding system / room, you may want the softer version versus a warm sounding room / system, you may want the other version.
Regarding panel azimuth discussions, I've posted a bit on this and you can search my posts. You can also use the "search" key with words like panel tilt, panel rake angle, panel azimuth, etc.
Hope that helps.
GG