Interesting....
The 14SG (which is essentially an 8FG with telemetry--they program about the same) uses a subset of the programming found in the 12FG/12Z/14MZ/18SZ/18MZ. The 14SG has less flexibility in its programming than the 18SZ. I love the 18!
For stiffer springs, just call Product Support and order two of these:
HSP79241 8M00F01702 ST-52 SPRING HD US0.85