If I want to end up with 100mm of COMPACTED crusher run as a subbase, how much should I lay down before compaction? Or to put it another way, how much does crusher run compact?
Put it on about 30-40mm thicker and belt the cr*p out of it till you notice the plate bouncing a bit like it were on a very hard surface. The main site has all the calculators you need to work out your quantities. You'll quickly get the hang of it.