A high-β hot-electron plasma was studied in an asymmetric magnetic mirror device with a variable cant angle. The plasma was produced by microwave heating at a frequency corresponding to cold-electron-cyclotron resonance together with a higher frequency suitable for upper-off-resonance heating. The position of the high-β plasma annulus was studied as a function of cant angle and was found to correspond approximately to the position of a midplane modulus-B contour. High-β effects did modify the spatial location of the losses of energetic electrons into the loss cone but had little effect on the cold-plasma losses. Destabilization was not observed when the line-tying of the plasma centre was reduced with glass end plates. An asymmetry of the cold-plasma loss with respect to the equatorial plane was observed at small cant angles and an electric field model was conjectured to explain this behaviour.