30% is a bit to high. I used to use a ratio of 1 part castings, 3 parts perlite, 6 parts soil. The mix still felt like it needed more perlite too. You really noticed it when you got to the harvest flushes! I since gave up and went to a soilless mix straight out of the bag.

Be careful transplanting rockwool seedlings into dirt. Ive had issues with the moisture variances between the two mediums (Rockwool holds on to that moisture!) that has caused some transplant shock due to root issues. Just a heads up, it's not detrimental! (All plants recovered nicely )

Good luck!