[Boatanchors] 300 ohm twinlead?

[StephenTetorka at cs.com]

Vic's point is my concern.
My 'dipole' is close to resonance on 80...but I use my 'tune anything' 
antenna tuner to match it to the xmtr.
But...I only use nominally 100 watts AM or SSB.

Now, I'd like to bring a homebrew linear operational.
It can put out 450 watts PEP and about 125 AM...into a 50 ohm dummy load.

Its my understanding that the line breakdown will occur from 'arcing' due to 
High Voltage.
One can hit the books..or use the standard capacitor air gap breakdown data 
which will suffice.
The twinlead dielectric ( plastic ) will increase the breakdown value.

Just wanted some experiential feedback.

Tnx,
Steve
WA2TAK