I got the oportunity to test out a 500mm reflex from Nikon. It's all manual, fixed f/8 and no stabilizer. I don't think I'll try this one without a tripod and you'de better have good lighting when you shoot with it because of the f/8.
But it's kind of interesting to play with so I hope for good conditions the next few days.
This image was taken with a rather wobbly tripod so I'll be looking forward to test it out with a sturdier one and a remote connected to the camera.