silly bit guard question

["Michelle Fink" <michrowe@frontier.net>]

I am trying to fit a 5" bit to a 4 3/4" mouth.  The reason being I am trying out a horse, and the bit I ordered is not here yet.  So will those round rubber bit guards make a too-big bit OK to use for a few days?  I know, dumb question, but I didn't think it was fair to experiment on the horse when y'all are so knowledgeable about these things.  Also, is there a type of bit those bit guard thingies work best with (full cheek, loose ring, egg-butt, etc.)?

 

Last of all, this horse tends to duck behind the vertical from previous training (I hate draw reins).  I will use a med.-large diameter snaffles.  Would a mullen mouthpiece be a better choice for her than a french link?  I have ordered one of the thick plastic apple-mouth french link bits.  I would like to help her get comfortable with bit contact.

 

Thanks!

 

m

(Colorado)