i use hpi aluminum c hubs and uprights at all corners, but the arms are kept plastic.

when you have a bad crash, the aluminum arms do not flex and might cause your tvp's to bend or break the bulkheads.( but the aluminum arms might bend or break as well)

think of the plastic parts as a fuse that is meant to break to save the expensive stuff from getting damaged, or so you can replace easy to replace parts instead of other parts that take long time to replace.

plastic parts also have a long life as they just flex back when they get hit hard, unless the force was way beound what any part would handle, then it is better if that part just breaks to save the parts it is fastned to.