How big of an issue is it when transplanting into 511, if you cannot get the medium from the previous pot disentangled from the roots? I just transplanted a pineapple guava tree which was completely root bound in the nursery pot it came in, and the roots were inextricably wound up with the medium so there was no way to rinse it away. I moved it from a 3 gallon pot into a 10, but basically there are still three gallons of the original medium mixed up with the roots in the new pot!