Op user:
I has not been fortunate one to have a SSBBW on top of me but the large ladies I had so far taught me this is the most intense position particularly when she makes the bed vibrate close to collapse.
JackSteven:
Yes, woman on top if you both can manage it. Hard on her knees and very difficult for him to breath. Feels excellent.
Only recently I understood why ladies fold their leg and put strain on their knees when on top. I like the lady to sit on me and extend her legs along my body while I caress her breasts.
I can provide the up and down motion and again the heavier the better.