Here's a tip for all players. Stop them from teching by disrupting their economy. Attack the harvesters. Focus on it whilst leaving 1 or 2 units across the pads. Be sure to destroy anything that tries to defend the harvester. If you do this right, the enemy can't tech, so no pesky sandstorm, no annoying rock worms, no troublesome centurions and no dreadful disruptor. I often do this in both my mock army (I steal the 1st missile then go kamikazi on the harvesters and their units, I don't care about the pads anymore after that) and my serious army. I pressure his economy so he can't tech and I win. If done correctly, your enemy would be too focused on his harvesters and he can't use the pads cause his units are dying before they can reach it.