Damien,
It's a fairly common practice, if you have a remote
tuner handy. How well it will work depends a lot on the
tuner, if it can handle the impedances presented to it.
Not having a remote tuner, I do about the same thing except
the coax run is very short and the parallel feed line is
very long (lol). Are there any 'problems' with doing it
this way (or your way)? Sure, the same ones you see in
almost any antenna installation. There are frequencies
where the RFI is more objectionable than others. What
those frequencies are is going to be different for every
installation / situation, so you'll just have to try it
and see. Good luck...
'Doc

Thanks for all the good info. gents.

Actually 80m is not critical for me. I was really looking for
something that will work nicely on 40 - 10m (including WARC would be
nice), and have been looking over the 44' design on the W4RNL page
http://www.cebik.com/aledz.html

The plan was to mount an SGC tuner or similar under the eaves near the
antenna and run coax back through the roof, because running open wire
feeder just isn't practical in the physical situation.

I run 250w PEP SSB, but it would also be nice if the system could
handle 120w of AM because I'm into that as well. Unfortunately that
means one of the high power tuners.

I have tried a Carolina Windom (40m "Beam" version") here, but while
it works well on 40m it gets progressively deaf above that.

H'm.... all food for thought.

Damien VK3RX

Open wire feedline is an excellent alternative and is much lower loss than
coax, especially at high SWRs. This way you can use a tuner in the shack.

73s,

Evan