I too have experienced low FPS with the SR22 ever since I purchased the plane. I bought it the day it came out. It is completely unflyable on my system.
I have a fairly high end machine:
SR22 version 1.1.1, Latest Windows 10, X-Plane 11.5 running Vulcan. RTX 2070 Super GPU, i7 9700 3.6 gig CPU. Z390 motherboard, 32 gig of DDR4 RAM.
I have tried turning my world objects to zero, no weather apps(clouds). The plane behaves the same. Major stutters that turn it into a .JPEG
I know you say this is not important, but every other aircraft, be it stock or third party, runs fine on my system with most sliders set up fairly high.
Please let me know if there is anything that can be done to rectify this issue.
When I do get a few smooth moments - it looks like it would be a joy to fly.