Topband: shunt fed tower - question?

[N2TK, Tony]

I am using a shunt fed Rohn 45 tower for topband. Presently I have one #12
copper wire 24" from one corner of the tower as the shunt. I would like to
try to increase the bandwidth. Presently the tower is 80' with 24' of mast
out the top with 4 antennas on it. Because I have a tribander side-mounted
at 42' the shunt feed only goes up to 40'. The feed point is 6' off the
ground. Presently I have a 50KHZ bandwidth for 2:1 swr. I am using 2 vacuum
variables to match - one inline and one to ground.
Figure I have two options:

1.Make a cage of wires.
If I do this is there a recommended size for the cage - 6", 12" or other
size?
I would think wire size would be immaterial for a cage?
Any advantage to having the shunt moved so it is off the face of the tower
rather than the corner of the tower?

2.Make a "T" with aluminum brackets at the top and bottom of the shunt.
I could make this the width of the tower. I would assume it should be off
the face of the tower.
With this method should I use 2 or 3 wires - ends and maybe one in the
center with 18" separation from the end wires?
With either method is 24" distance from the tower a good starting point?

Since there is snow on the ground figure it is a good time to start antenna
projects - hi.
Tnx for any feedback.
HNY
N2TK, Tony