Sorry for double-posting, but I managed to work out what I was doing wrong, and I now have my Jolly 5 IV Gible! First of all, I decided to get off my lazy butt and figure out the exact IVs of the original Gible (I already had the IVs for Tyranitar), as well as figure out what delay I hit. I found out that I had hit a delay of 950, well off of the 961 that I was aiming for. So, in EonTimer, I put 950 into "Delay Hit" and clicked update. EonTimer gave me a new calibrated delay of 479. Another thing I remembered while looking into this further; prior to attempting to RNG, I watched a couple videos by bearsfan092. While I wasn't able to fully understand the HG/SS breeding video (possibly because he was going after a shiny, which I wasn't), I did take note of one interesting tidbit from the calibration video: the player could hit only even delays or only odd delays depending on whether a Generation 3 cartridge was in the Advance slot. So I tried again with the new calibrated delay, with the Advance slot occupied and unoccupied. Unfortunately, I was still not getting my desired results. So, I searched for what delay I hit for one of the non-Advance slot results, as my target delay was odd, and the 1st attempt hit an even delay. This time, I was hitting a delay of 967, which upon being put into EonTimer, gave me another new calibrated delay of 483. The very first attempt with 483 and no Advance slot was successful. So...thanks to everyone who contributed to the guide and to RNG research in general!