Blending/Creating a Surface Between several trimmed edges

I am quite new to Rhino and needed some advice on how to blend or create a new surface between two existing (trimmed) surfaces/edges. I have a human model here and after some tweaks and rotations the ultimate goal is to achieve a smooth body with no open surfaces, holes or exposed joints for CFD analysis.

However I’m finding it quite difficult to close the surfaces and thus create one continuous body and wanted to know what could be done here. I’ve tried blending, matching, merging and joining all to no avail (possibly due to inexperience). I’ve attached an image of the first region I’ve been attempting to merge (the abdomen precisely).
Thankyou in advance


Ah sure,
The file is too large to upload even as a zip file so I’ve attached the link to the original body (which is pretty much still the same as my edited version) I got from grabcad. I used the first model (on the left) from adam closed group file.

Thankyou again

Ah I actually messaged the creator of the model who replied saying it would be very difficult or near impossible to create a smooth model in the way in which I was hoping for (something like the second (middle) body from the Adam closed group file).

Ah wow, amazing Richard! Trying this right away. Could I use the same techniques if I then wanted the abdomen to extend outward towards the first layer of the model? I.e making a smooth continuous surface between the upper abdomen edge and the hip edge?
Thankyou for your help

Ah perfect, would explain why matching never worked the first time.
Thankyou very much for this