I've put the mag in a couple different locations in different airplanes. Space is sometimes an issue with some as they're kind of tall. If you're using Garmin and you have a problem, they will want you to move it to their recommended location.
Pick a couple different locations and pull spare wire there for easier moving if you have problems.
The one place I've had some success besides the wing tip and the recommended Garmin location is above the aft bulkhead access panel especially if you've moved the hyd pump behind the seat