Yes, my question is how, and how does the spring not over compress when you merely cut the legs off the solid follower and put in 15rds, since the 15rd Mec-Gars have a hollow follower that the spring goes up into. It seems to me you would need to not only cut the legs off of a 13rd follower, but also hollow it out with a grinder to achieve the same result.
In fact, since the spring is already at the bottom of the 13rd follower, how does it not over compress with 14rds. My only experience with this is Mec-Gar 20rd BHP mags. They seem to accept 21rds with approximately the tension of a fully loaded 13 or 15 capacity Mec-Gar, but I don't know if it's wise to do.
And I've used a lot of mags of different manufactures, OEM/MDS/Checkmate/MecGar that seemed from the outside and even inside appearance that the springs should be compatible with the same capacity mag as far as compression, but they aren't.