Offset B-Rep/ How to create flat surfaces only

Hi,

my question composes of two parts.

1/ in my Gh definition, i am trying to offset the brep by the radius of the structural piping (so that the skin sits flush with the outside of the piping). i plugged a number slider into the 'd' input, but i get the following error message; SOLUTION EXCEPTION: OBJECT REFERENCE NOT SET TO AN INSTANCE OF AN OBJECT.

2/ I was wondering if there were a way to 'flatten' surfaces. at the moment, my surfaces are flexy, as if made of a fabric. imagine if you will, that the surfaces are made of ply. for this reason i'd like to have the surfaces made of triangles or something similar. any clues on how i can do this?

thanks in advance!

eva