20 inches and you went to the park. I hope your tolling as that'd be better than skiing park when you can ski 20 of fresh.
Anyway, the reason you edges cracked is not bad construction, its you.
Your edges start as a (relatively) soft and ductile material that will dent and ding when it hits rails. The more you hit rails the more the edge will work harden, making it harder for the edges to dent and ding more (the yield strength of the edge increases the more you hit it).
This is not a good thing for park skiers. As the edges get harder/stronger they also get more brittle. Eventually they get to the point where they will change from behaving like a ductile material (that dents, dings and deforms) to a brittle material which cracks.
Once your edges have cracked the way the adhesive between the edge and the ski is loaded changes and becomes much more damaging. As a result the adhesive will start to fatigue and will fail much more easily, i.e. your edges pull out.
If you want to prevent this happening at least get a diamond stone and take off the hardened steel on the edges after a good bit of rail action. Preferably get a shop to go over your edges every so often.
It is in the hardened material on the edge surface where the crack will initiate. Once that crack gets to a critical size it will go straight through your edge in about one and a third milliseconds. It does not matter how thick your edges are, once that crack propagates its going to go all the way through, whether your edges are 1 millimetre thick or one metre thick.
If you remove the hardened material on the surface you'll remove a lot of the microcracks that can initiate a crack through the edge. You'll also reveal softer, more ductile material underneath which is less likely to crack.
