Thanks to all you guys for your responses back on this.. It's given me lots to consider the next smoke with regard to spare ribs..
To answer some of your questions of my setUp here, I do not have a rib rack (have considered buying one), so laying the ribs out flat.........which is the main problem due to the tips being in the edge of the smoker where it's much hotter.. Also, yes there is sugar in my rub (Jeff's Rub I purchased from him online........good stuff!).. The temps that I usually run is right at 250, and despite all I've heard (and believe) from folks posting about the temp deviation issue from the factory therm and a "grate level" thermometer...........the temps are ALWAYS the same.. I've checked this multiple times.. Really don't know what else to say on that issue except maybe I'm lucky on that one...:).. I use a water pan full of water each time I smoke too, so should have plenty of humidity inside smoker..
In the future I will definitely move the ribs around some on the smoker.. Before when I had this problem I didn't touch them, since it was my first smoke of ribs, so a bit on edge about it..........leaving things in place.. Time to experiment I think!
Thanks again, and if you have any more suggestions given the above additional info, please let me know...