I've been having problems with gauges looking torn and pixellated when I dragged them to my second monitor.
It turns out that in FSX Settings I had that monitor set to 1024x768, instead of its native resolution of 1680x1050, so no wonder the gauges were looking big and nasty.
I feel pretty stupid as I had set the correct resolution of my main view display, but after adding the second monitor I hadn't thought to use the dropdown to select the new monitor and set the correct resolution on that one as well.
Still, it's working fine now :)
I spent a couple of hours last night configuring the new RealityXP Flightline T gauges on a custom panel with a black background in the default C172. I was trying to get them to display at 8cm x 8cm so I could cut some holes in a plywood mask to allow them to show through.
Because of its age FSX assumes all monitors are 4:3 and consequently round gauges appear oval unless you edit their size in the panel.cfg.
After some experimentation I got the basic six FLT gauges displaying correctly in full screen on the second monitor. They're still not perfect, with some minor tearing on some of the instrument markings and lettering, but they are a big improvement on the default gauges.
Next step is to create a generic default panel that will work for all the single engine aeroplanes in my hangar, then do the same for the twins.