Most machines I see in my part if the world have the two shields over the bevel gears removed, as described by Unit 2.

The zip tie solution isnt great, but helps.   The problem is straw and chaff gets packed in there, and then  any  spill from the tank filler directly above soaks it all in diesel.  Shouldnt happen, but the real world  sucks.. 

A heated bearing then  will set that area alight quick smart. You likely will smell something before it is un-recoverable, and then you have  about 25 seconds in which to deal with it. 

You can do NOTHING about it with those shields in place. As an acquaintance of mine said.." grab your lunch box, and go sit away from it, and watch it burn while you eat".

Id suggest that on any shields you remove, you write  on the back of them with a marker pen  where they came from, or at least which side and front or back of the machine, to aid in replacement down the track.

Most of the rest of the shields on  21 Series are reasonable to deal with, and shouldnt need to be permanently removed.