Is there a way to get a 'hexl-insert-hex-string

[Mac]

I've just started to use hexl-mode to edit binary files and two
things makes my colleagues say emacs can't do everything (I wonder who
gave them that impression in the first place;-).

1) When starting hexl-mode, I can enter characters directly, which
   works great. But, when entering hex, I need to run
   'hexl-insert-hex-char' or 'hexl-insert-hex-string'. 

   Is there a way to get hex nibbles inserted automatically? Sort of a
   'hexl-insert-hex-nibble-mode'? So when I type [0-f] that nibble is
   inserted directly, just like the character is when I start
   hexl-mode.

2) Is there a way to increase a files size with x number of
   bytes/chars/whatever?

/mac

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