1/4 wave elevated ground plane antenna

Hi folks

A couple of questions on this antenna I have put together. It has a top section using a s/s whip,
4  ground plane elements of copper wire, all 102" long mounted on a plastic pole 25ft. above ground.

1  If I swap the plastic pole for a aluminum one, what effect would that have given that it would 
be connected to the the braid side of the coax?

2  Run the coax down the inside of the metal pole to ground level, would that decrease common
 mode current (noise)?

Thanks
Pete

1) Hopefully none at all as the ground planes are doing the job they're supposed to be doing.

2) Not a guarantee. Using a RF choke at the antenna feed point though would be a better idea.