PRO-MIX REVISITED?

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I have a few 15 gallon containers that I am intent on planting this year (tomatoes). While I have noticed numerous opinions on what makes a good and/or great container mix(s) everyone seems to agree PRO-MIX, if available, makes for a good growing medium. I am unable to locate the PRO-MIX BX but have found one of our local big box stores that carries the PRO-MIX HP. The only difference I can see is that the HP is higher in perlite. Would this be an acceptable substitution for the BX? Also, I was curious as to if it (the Pro-Mix) would be best mixed in a 3-2-1 ratio (Pro-mix, bark fines, perlite). With the additional perlite in the Pro-Mix HP require a reduction or even eliminating the 1-part of perlite? I have a source for bark fines and perlite but would hesitate to use them if you think they might not be necessary. Also, my neighbor has a 20lb bag of “Black Gold” worm castings in her garage that she has not opened and has been stored for 3 or 4 years. Any problem using them after storing for a while. She wont use them so they are free for the taking. Cant get better then free. Thanks.