Alright so it's been awhile since I posted this but I've made some changes to my technique since doing so. Mainly I've switched from using Blue Gasket Maker to Black Gasket Maker as it appears to be much more resilient to breakdown and seal failure as well as it is easier to clean up if you have to re-seal a mag that was already sealed before but sprung a leak again.
Also I've stopped using the black rubber gasket that comes with the mag, I simply toss this out and apply a hefty bead of black gasket maker and then attach the back plate to the mag once again, being careful to screw it down evenly as to ensure the seal remains intact.
From what I've seen there seems to be less failures with the black gasket maker compared to the blue. The only downside is it's even harder to pry the mag apart, in fact I've ended up cracking two mags doing so, so beware, it works real good!
Also for those friends who I have mags of right now to be sealed still, fear not I will get to them but I have recently moved to Aurora and have not yet set up my workbench. I intend to address that issue this weekend so I can start working on these things again (and so I can start reloading again!).