Prepar3D V4 Stutter in Oculus Rift, not on screen

Hi all,

My first post so hope you can help. I am based in the UK and recently assembled a VR flight sim with our apprentices to take to STEM events and college open days representing the company I work for. The PC Setup has an Asus X370 Gaming MOBO, AMD Ryzen 7 Processor, 16Gb of RAM and a GTX1080i Graphics card connected to a cockpit with HOTAS flight controls and an Oculus Rift Mk2 from the HDMI port on the Graphics card and a small 24" HD monitor attached to the displayport output.

We installed a Professional Plus version of Prepar3D V4 and enabled Virtual Reality, the desktop screen was set to single image. We also downloaded FreeMeshX maps of the UK and added them to the library.

On first glance, it looks fantastic and the VR is rich and detailed. However there are noticable stutters in the terrain, especially when the Oculus headset is moved to view lateral movement. The stutter is much more visible in the Oculus Rift and much more stable viewed on the monitor. This is much worse when flying at high speed in an F22 Raptor.

I have tried the following;

turning all the graphics settings down to low and mid.

lowering the frame rate incrementally.

disabling the 3rd party maps.

Removing the reflections in the ownship.

Adding a second GTX1080i connected with an SLI bridge (this actually made the stuttering worse).

None of these cured the stutter but did alter the severity.

The CPU usage isn't maxed out, not tested the GPU usage but I reckoned that if the stutter got worse with a second 1080, it probably wasn't that.

The temperature within the case hadn't got above 40 degrees and cooling was working well.

What I am wondering is if anyone else has had this problem and how/if they fixed it or does anyone else have any suggestions on what I can try next. There are no visible error artifacts on the terrain and the sim works just fine in every other respect, it is just a shame not to show the software off to it's full potential, especially after the apprentices put so much work into it.

best regards

Rich.