Javier,
Now I've got a while to answer for your questions.
If about my trinocular head you could see it thanks to Charlie who gave the link to one of my posts
As you could see it wasn't the trinocular head but simple tube with horizontal eyepiece. It wasn't parafocal construction. First I looked over the slide through the horizontal eyepiece. When I found something interesting I had to stand up and observe it on my Pentax camera monitor. I had to align the focus looking straight at the monitor. It wasn't comfortable. Additionally because of the tube length the image on the monitor was only the part of regular field of wiev seeing through the horizontal eyepiece. As you can see using my device wasn't easy. But there was one advantage - I could see exact frame of my final result.
Last days I managed to buy the real trinocular head at Polish auction

. Thanks to it my work became more comfortable. I can observe the slide both of eyes. It is really comfortable. But until now I haven't tried to set parfocality. Force of habitat is stronger
The length of my new head is smaller than the previous one so at the monitor I can obtain the imege almost the same like in the eyepiece. Perhaps somewhen I'll try to align parfocality but now it is not so important to me. Charlie gave you already a lot of advices if about parfocality settings.
If about phase contrast:
I haven't used it for last year so I forgat a little. But it is not so difficult. I must back to this method to explain you exactly everything. I'll try to take some photographs presenting various results depending on degree of rotation the ring in phase device.
Your Lumipan is older than mine indeed, but not too much I think. The most important for the image quality is quality of optics and not model of microscope. But new microscope give us the prime quality of mechanical parts which is very important for convenience of our work
Now I'm enclosing some photographs with my new trinocular head.
It allows or observing sample through the eyepieces or through the camera, not simultanously.
Suwalki, Poland
Best regards
Marek Mis
Suwalki, Poland