Just thinking out loud Tom.  Perhaps the missing half of the sloper 
is inadequate for 75 meters.  Perhaps the angle of the wire effects 
the minimum SWR.  But, how does the antenna work?  If you didn't know 
that the SWR was high would you suspect that your compromise antenna 
is letting you down?  Can you wangle enough space to get up a 
temporary 75 meter dipole and be able to switch between the two wires 
to see the difference?  Would that tell you anything?  I believe that 
you have found that adding coax to the feed line lowers, in theory, 
the SWR.  I guess what I am asking is are you being misled by an 
arbitrary meter reading that may in fact not mean too much.  And 
certainly I can be wrong as can be and that your gut and your meter 
are telling you that the antenna stinks!
To end all of this rant; when I was a kid in the hobby I put up 
antenaes cut to a quarter wave, particularly on forty meters 
according to the formulaes and, knowing what I know now, they were 
probably way too long since they were pretty low.  But I didn't have 
an SWR meter.  I had a Windem fed with 300 ohm TV twin lead which I 
now know was an awful match but the PI network forced power somewhere 
so I was convinced that I had a great antenna.  I guess that 
ignorance was bliss!  Perhaps if there are other hams in your close 
area, you can work QSOs with them and see at a distance how your 
signal compares.  Okay, I'll stop sounding like an old fart!!
Good luck my friend.  Antennaes are really a fun part of the hobby.
Pat, K9JAUAt 08:22 PM 11/27/2012, you wrote:
>Hi, all.
>
>Please forgive me, since I know this antenna  has been discussed on the list
>before in various forms.  But, I am needing some basic info from the
>perspective of someone who has actually used one.
>
>Here's the deal:
>
>As some of you know, for reasons I can't quite understand, I have been
>having trouble getting my W8AMZ 80-meter half sloper to work well on 80
>meters.  The SWR's for most of the band are at least 3 or 4 to 1, except for
>about 100  KHZ between 3.850 and 3.950,  where they are below 2.1 to 1.
>Based on the better luck I'm having with the 160-meter sloper made by the
>same company, I'm convinced that there is either something wrong with the
>antenna, or something in my installation that is throwing things off.  Tom
>(W8AMZ) himself has actually volunteered to come to my home QTH sometime to
>try to assess things.  He is about an hour and a half from me, so it's a
>trip that will have to be planned by him when he has the free time.
>
>Since I'm not sure when that trip will occur, I'm thinking about other
>alternative antennas that might be easily put up  and relatively
>inexpensive.  I don't have a lot of room to put up another antenna, but I
>probably could handle  an antenna that was approximately 100 feet in length.
>Again, my main band of concern is 80 meters.
>
>I believe that some folks on here have used an antenna called the Cobra, or
>Cobra Lite.  If you have used this antenna, could you please describe it to
>me, tell me how you put it up, state any special installation considerations
>I might need to take into account, and tell me whether it worked well on 80
>meters?
>
>I am not sure of the price of that type of antenna, but I'm sure I could get
>that info from the Cobra web site via a google search.
>
>I simply don't want to spend money on yet another antenna, unless I have
>some assurance from someone who has actually used it, that the antenna might
>be a good alternative for me.
>
>Thanks, and 73 from Tom Behler: KB8TYJ