The trick with the X-Ray 808 is that the engine sits at an angle to the spur gear, so a square mesh is not possible - close but never square.
Just run the set up with quite a bit of clearance in the mesh and you shouldn´t have a problem. Quite a bit of lash lets the clutch bell sort of float on the angle and doesn´t seem to wear the bearings or gears at all.
My Avid Revolutions clutch bearings last just as long as anyone elses bearings with a conventional square mesh. Plus the X-Ray bell bearings being a larger size cuts down on wear too. Could be too much power from the MG66 is the main cause Gizz