Mike,
I don't believe that any performance would sufffer but you would 
likely see different tuner settings.  There are sharper knives in the 
drawer than my knowledge of antenaes, but I am hard pressed to 
imagine that you would be hurting yourself.  If that happens, worst 
case, you have to drop the vertical and remove the top 
wire.  Inconvenient certainly.  But it is something that has to be 
tried to see what happens.  What does the manufacturer think?
Good luck.  It is already mid-twenties here, windy with a forecast of 
a couple of inches of snow overnight Saturday.  Ideal antenna work conditions!!
A friend and I once, back in the day repaired an antenna on a well 
below zero afternoon!!  Back in the day when I was known to have a 
taste now and then!!  Took more than a few beers and shots of C C to 
get that job done!!
Good luck.
Pat, K9JAUAt 01:29 PM 11/13/2014, you wrote:
>Pat:=20
>
>Would adding a length of wire to the top cause the other bands to =
>suffer? If so why would this be the case?=20
>I really don't wanna kill my 40/10 performance. More in particular, 40 =
>and 20. I occasionally take a trip up to 17 and 15 but mostly hover on =
>40 and 20.=20
>When choosing the vertical, I got it with some pretty good performance =
>on 75M in mind, which it did do until the tuner break down.=20
>So I would like to add a pretty good 75M to my 40/20 and occasional =
>17/15. LOL=20
>
>73:=20
>Mike VO1AX=20