I always use 33-40 percent. Currently i am in compost and i mixed 40% compost, 40% Perlite and 20% peat. The plants seem to really like it. Some of those promix blends have a bunch of perlite in em though dont they? which one are you using?
Using the Premier Pro-mix, it does have perlite i mixed in, but not a bunch. The guy who got me on to pro mix got back to me and said 1-1.5 of perlite and 3.5-4 gallons of pro-mix for 5 gal bags.