That's not too bad on a single 6S pack!
Luke has a point... it may be time to sink another 59 into a new pack...
also as odd as this may sound to some people, I have begun using 2 pieces of 1/16" ABS plastic when I build my packs... I clamp the packs within these ABS plastic "end caps" really just rectangular pieces the length of the packs then I wrap them in extreme duct tape before releasing the clamps.
End result is that since Ive begun this "process" (ghetto as it is) i've not had a single expanding battery due to heat and the temperature of my newer packs is 10-15 degrees f cooler than my old loose sided packs.
I assume this is due to the factors luke mentions above but I had no idea when I started doing it, I just didn't want to see the outter cells swell anymore = )_
I've been doing the same thing 5lbs of tension on the electrical tape as I wrap a stack of packs, and I do 10 wraps in 4 places. It works out to be 200lbs of clamping force on the cells.
I played around with an old seriously abused (drained to 2v, over charged to 4.5/cell, lol) helicopter pack that was badly puffed. It was more like a sausage than a brick. lol. I hooked up my ghetto halogen bulb load bank with a voltage meter on it, and put the pack into my vise and started putting some pressure on it. The saggy voltage jumped up like 2 full volts when I put some squeeze on the layers I worked it out to have cut Ri by something like ~80% over no clamping on the poor damaged pack.
Packs like to be squeezed Just not so hard that the layers short inside