There probably is some way to get a flat field on the PST, but it may take a long exposure??? My PST's sweet spot wasn't centered, so maybe that's why the gradient is offset on your photo. Of course, the sun should appear darker towards the limb naturally. A nicer result that when I had my PST!

Thanks Drew. I use a Baader Hyperion 8-24mm EP that has a thread on it, that with an adaptor I can hook straight up to the t-ring. You are right about the brightness. I plan to have a play around with gradients one day. Not sure if a flat frame is possible with a solar telescope? This was right in the middle of my frame. Maybe the sweet spot with the PST is lower down and to the left by the looks

I like the two exposures blended. The overall brightness profile looks a bit offset (likely due to positioning in the FoV of the PST?) Did you use afocal projection or have you found a way to make the PST reach prime focus?