Mesh handling has improved significantly (at for example Windows Build 928) with an “Edit” -> “Edit Properties” capability accessible by “holding” the mesh object after it is rezzed (left or right click on it seems to work) and hitting the edit properties hot key (` by default.. the key to the top left of a UK keyboard not the usual single quote symbol).
A video showing the use of the tool created by Chris Collins at High Fidelity is available at