I agree with Irv, I used 300 ohm tv line availabe at Radio Shack, Home
Depot and Menards for 25 years, on an 80 meter dipole. I used several
different tuners WITHOUT a Balun and fed the line directly. You can even put
a couple of short leads on a PL259 and splice it to the Twin line if the
only output your tuner has is an SO239.

For your next tuner, watch Ebay and buy a Johnson Matchbox for under $100.
They will match most loads you are likely to encounter, and are designed for
Balanced line.

I presently use some home made 450 line on a 60 meter (90 foot end to end)
dipole, as that is what fits between my trees. I modified my Matchbox to
make it load all bands with the 90 foot dipole, but you can get the same
effect by changing feed line length if you have "problem bands".

Reg Edwards, program Dipole3 will let you calculate the difference in losses
between the 300 and the 450 line using the actual hieght and length of your
dipole.

http://www.btinternet.com/~g4fgq.regp/

KA9CAR