I use my tv eyepieces in all my scopes. Never notice field curvature unless I look for it. Of course most are f8 or longer. For that matter, I never notice it with my Brandons either, unless a planet drifts to the edge. Of course my astigmatism is so bad, that might have something to do with it:-). Seriously, even with my observe’n glasses, it is not something that jumps out at me. My eyes are going on 52. Different for different folks.
Try sub F/5.5.