Uneven chamfer of solid edge?

Hello there,
I’m a new Rhino user (just did a course a few weeks ago) and I"m no working on my first project. I have a solid that has got irregular and rounded sides, but flat (planar) top and bottom faces (bit like a section of a tree trunk). I need to add a chamfer to the bottom edge, however it has to be uneven, i.e. the trim to the side face needs to be small, the trim to the bottom face large.
The “chamfer” tool in solids only does even, 45 degree cuts. I tried to extract the surfaces of the solid and use the chamfer tool in surfaces (where you can adjust the chamfer distance individually) but here the problem is that the transitions from one side surface to another cause lots of problems and it goes all over the place.
I also tried to do 1 Rail Sweep, using the silhouette of the top edge as a rail and a manually drawn chamfered edge as the shape, but again it goes all over the place when it goes round the corners.
What can I do??

Try with exploding and then trimming the vertical surfaces with a horizontal plane that is higher up (+z) than the bottom surface (or scale 1d). Then offset the border (dupBorder) of the bottom surface to the inside. You’ll probably have to clean up the resulting curve (check for self-intersections). Then EdgeSrf two and two edges.

Thanks for the reply! I did a mixture of a few things in the end: I used a surface chamfer, not the solids chamfer so i could do it unevenly. That resulted in a lot of unwanted effects (areas of the surface folded over, overlapping/overspilling on the edges etc). I then trimmed all excessive surface areas and then re-traced the resulting lower edge with a clean curve and then lofted the original upper edge curve to the new bottom one. A lot of extra work, but it did the job.