Performing Minor Edit in STL

[bzowk]

Hey Guys - I've got a model which I made (well, honestly assembled from other sources) within TinkerCAD which is two hands on a desktop stand (see attached). Due to preference as well as the size of my printer bed, I'm wanting to shorten the wrist of each hand. Having used CorelDRAW in the past, I thought this would be simple; but cannot figure it out despite trying it in a variety of software including TinkerCAD, Meshmixer, Blender, FreeCAD, & 3DS Max. Thought I'd post here as I'm sure it's simple once you know how to do it.Any suggestions? Thanks!