[Jonny250]

If you use the recessed track then i think you reduce the vertical stiffness of the gun quite significantly - if that might be a problem? in the image of the 2 tracks the effective thickness (for stiffness) is about 1/4 less on the recessed track, so 0.42 x the stiffness...
I like the idea of the enclosed the track for hiding the bands - reducing that vibration when you track sideways...