@jfg 

Wow I can't believe I didn't think to change the bitrate in my formatting, thank you for this suggestion! I'm converting it now and then hopefully I can have a go at changing the parameters I wish to change. I might be back to ask some more bits regarding when it comes to parameters to change but this is a great help and thank you again so much.

A number of systems (youtube included) simple give you a predefined selection of thumbnails to pic from.
So perhaps a default of position 0% as it is, but with the option of changing a thumbnail to use 10% 25% 50% or 75% as alternative thumbnails.

Please submit a ticket so we can get this logged in our database.

Good find!