media re-amend container media

So I've got some numbers on re-amending my container mix for the second year yet I can't remember where I got these numbers.
For every gallon of soil 5 ounces of aeration and 5 ounces of compost. 10 gallons of soil would then need 6.25 cups of aeration and 6.25 cups of compost or .4 gallons of each, using the idea of 1/3 peat, 1/3 aeration and 1/3 compost for the original mix. It actually seems a little light to me.
i think the 1/3 of total volume of compost may be a little to much. its bad for drainage which is essential in container growing. i have heard here that something like 5 parts potting mix, 2 parts perlite and 1 part compost. i`ve also heard it stated as compost should be around 15% of total volume media.