Went ahead and installed the simple 100V solar controller. It takes 12 volts and the pack voltage. When pack voltage reaches a set value, it will disengage a relay. It's set to disengage at 88 volts, which is a little over 3.5 volts per cell. The relay then controls the Elcon/TCCH charger's Enable pin, which will instruct the charger to stop charging.
Of course as the pack voltage drops, the controller will re-engage the relay and the charger will resume charging. This will make the pack voltage bounce back and forth pretty much forever, so it's not a perfect solution, but it should make sure the charger doesn't overcharge the pack right away. On the other hand there's no CV phase, so the bouncing is kind of necessary to get the pack full.
In any case, this solution will have to do for now.