I'm using a Cannon HV40 with a Juiced Link Camcorder XLR Adapter/Preamp/Mixer
CX211. To record sit down interviews "talking heads".

I have inherited two cardioid microphones: a Sennheiser K6/ME64 and a Sony ECM672 microphones.

Am I going to gain any advantage from plugging both mics in to record an interview with an individual? I've used both to record an interview with two subjects but I mainly do interviews with one person at a time.

As I'm new to this does anyone have any suggestion as to the best mic to use out of the two as my primary mic? I'm thinking that I'm covering any potential problems by having two plugged in, but does having either one plugged into the 1st XLR Port make it the primary mic?

When doing such interviews when it's shot in a quite room, where is the best place to position them in relation to the subject? I first thought putting number 1 one a stand at about knee height pointing up at the subject and having number two attached to the camera which would only be positioned 1.5 - 2.5 meters max away from the subject.

If using two mics does bring advantages what should the settings (low, mid high) and trim for each mic be set at in order to achieve the absolute best sound recording possible when conducting "talking head" styled interviews with this set up?

Any advice would really appreciated!

The best position for a microphone is as close to the subject's mouth as practical.

You NEVER use the sound from more than one microphone recording a person talking. If you record with more than one microphone, then you must listen to each different track during editing and decide which one is better. Use the good one, and the other one is only a backup if something happens to the better one.

The other thing about having two separate recording tracks and mics, is you can record one at a higher gain, and one lower, and if there is a situation where the higher gain recording distorts, you still have the lower track. However, what most do in that respect is just have one mic, and still set one channel lower than the other to accomplish the same purpose. I would choose the best sounding mic, and record the single mic on both channels, with one set a bit low. As alway, monitor what your camera is recording with headphones.