I’ve always found the sitting position better for bigger patients.
But as soon as you swing the pt’s legs off the side of the table, you lose much of the benefit.
I get someone to help, then make the pt do a sit-up, with the legs straight out and still on the table. I go to the head of the table, get prone (almost), rest on my elbows, and I get the best curve of the spine at the target level that you will ever see. Added bonus, after you get done, all you need do is lay the pt straight back down. No swinging the legs.
Can’t do this alone though. The pt is vulnerable to falling off the table, admittedly, but in >25 yrs doing that way, that has never happened. Could though, so be cautious.
Also, obese patients and the elderly need some manual “encouragement “ to bend in the “sit-up” position. But it does work.