What I have gleemed out of this thread is, to get the best efficency I should match the feed line to the loop at the feed point.
In that case I haven't made myself clear enough.
As Cecil said, given that you are using ladder line (the ARRL numbers understate losses -
the Wireman 551 - 554 numbers in VK1OD's calculator are probably more accurate) then
the losses will be low anyway, even for multi-band use, assuming you are using a good
tuner in the shack. In that case the loop doesn't have to be exactly resonant and the
antenna will still work well. With your balanced tuner, you have a very good multiband
system and there isn't much you can do to improve performance (without changing
to a different antenna or getting it higher.)
Where the matching is important is if you are using coax feed to the loop, since a high
SWR will increase the losses to a larger extent.
The truth is, if the loop is close to resonant on 80m, then just about any sort of coax
feed is fine for casual operation. With 100' of RG-58 your losses are less than 2dB.
In many cases that is good enough. The real issue is when the loop isn't close to
resonance (sometimes you have to just put up a loop where it fits without the
luxury of pruning it) and/or for multiband operation. In those cases, ladder line
feed is generally going to be more efficient. The 4 : 1 balun approach provides
a practical alternative for multiband operation at good efficiency with direct coax
feed to the antenna as long as you can prune the wire to keep a reasonable SWR.