Hans,

I don't think it's worth it. The patterns and ground loss of the two
antennas at a height of only 35 feet are really very similar.

On the other hand, the impedance of the full wave loop according to
EZNEC is going to be around 100 ohms resistive, while the 100 foot per
side loop has an impedance of about 1500+j3200 ohms.

I'd recommend saving the extra 120 feet of wire for other antennas and
just building the fullwave.

Now, if you want to use the antenna with a tuner at the feedpoint or
perhaps open wire feed, the impedance of the 100 foot side loop on 160m
is much more reasonable (64-j1300) than the 70 foot per side loop
(EZNEC reports 8000-j30000! that is to say, infinite :-) )

73,
Dan