HIP106890 Elephant's Trunk Nebula

Anyone has got any tips regarding the atrocious vignetting inherent on the TAK FSQ85ED OTA? Currently using the x0.73 reducer, looking at purchasing the x1.01 flattener, to see if that makes things better. This image has 30x300s + 60x180s subs using the L-eNhance filter. Plus BIAS/DARK/FLATS to go with it. It's also my first ever image processed entirely using Pixinsight and very mildly touched up in Lightroom. I'm very happy with it but, as always, simply stepping stones in a very long learning curve. Any feedback welcomed!! Image taken from Bristol (BS4), UK at Bortle6