The reason the recipe works so well is because it holds lots of air and good amounts of water, instead of too little air and too much water. Replacing the PB with sand would be something akin to replacing the air in a football with water. It's going to have a significant impact on suitability.

The only reason the peat (or you could substitute compost) is in the soil is to adjust the water retention of the PB. IOW, if the pine bark was very fine (like Fafard's Aged Pine Bark, you wouldn't need the peat or compost. If the PB was extra coarse, you might need more peat or compost.

Sand doesn't impact drainage of a bark based soil very much, but it does impact aeration in a negative way. It's my considered opinion that aeration is the most significant factor that delineates superior soils from 'eh' soils. From the perspective of growth and vitality, there is almost no such thing as too much aeration. It's only when you factor in grower convenience and the reduced water retention that accompanies highly aerated soils that we hear complaints about highly aerated soils. If you're willing to water a little more frequently, you can have extremely healthy plants with less effort and a greater margin for grower error in highly aerated soils, as compared to heavier, water-retentive soils.

Sand, because its physical and chemical properties are so much different than PB, can never really replace the bark.

Al

Boy, Al, you were right on top of that one.

kawaiineko, as we explained in your other thread, the topic of this forum is wintersowing. When the seeds in our containers sprout in spring, we transplant them, usually as tiny seedlings. Our plants do not spend their lives in their origianal containers. Because of that, growth and performance is probably not affected so much by the soil.
Most of us, by far, use commercial potting soil rather than mixing our own. So this forum might not be your best source of information for growing plants in containers long term.If a plant is going to stay in a pot for a long time, the soil needs to perform better for a longer period of time. Have you read our FAQ as recommended to understand what this forum is about? So you would probably can see that you would get better information elsewhere (the container forum or th soil forum) for plants that will spend their entire lives in a pot.

Around here (gardenweb) Al is pretty much regarded as the expert on soil mixes for containers, and he has given you his recipe in the past. Have you read is famous threads about perched water table and movement of water in containers? If not, I recommend it highly.

Are you using the 3 earthboxes that soilguy2 bought for you? What soil is recommended in the instructions?

Karen