Please be aware that my kitfox is still under construction and I've yet to actually mount a magnetic sensor on the shelf and put it to use. When I do I might discover some things I should have done differently.
As I previously mentioned I fly with a Dynon unit but I don't know how it compares to your MGL unit.
I had to mount the compass module out in the wing tip to avoid the influence the steel fuselage would have on it. I have included some pictures of my install. The module has specific requirements for direction and attitude so I built the installation with adjutment features in 3 planes. My plane has been flying since June of 2010 and I have good performance of the compass feature.
The Dynon unit has other sensors in the instrument box and that box is mounted in the panel with specific attention to the direction and attitude, but it doesn't have to be in the center of the plane nor does it have any requirement regarding the steel fuselage.
Just bought an XTrem and SP6 and SP7.
For the moment only put the SP7 i put it between panel and firewall and it's ok nice product. No time for the moment to install the SP6 compass will be harder to do metallic environment
if you guys need to null a magnetic field ,..there is a product called "Magshield" I've used it to block areas around a compass and electrical components,.. it is basically a high nickel alloy,.. for the life of me i can not find the paper work from when I last ordered some or I could give you the vendor,..maybe a google search?