err well considering how fast alliance allegiance can change and any solo can 'suddenly' be allianced...
I don't think limiting your search to find only solo targets is what you should concern yourself with....
why not just make a list of solo id's and just put them in your search for box
(sure, you won't find someone new, BUT, you wouldn't be able to tell if any of your 'not id' list had fallen into the solo categorey)
if it's safelists as alci suggests, i suggest a different game.
otherwise when you find solo targets just make a player note so you can hover and do tooltips. surely the range of targets you are looking for do not span your 30% to rank 1.
If it does, then please, do yourself a favor and narrow your search to a specific band / range. Can't find a target in that band, then move it. Switch out alliance ID's based on your score range.
But really before I say I'm for it or against it, how many id's did you put in there and how many are you trying?
If azzer extended the range 1 id space, then he'd fulfill your request adequately and correctly, but maybe not what you wanted.
Specifics plz.