When I speak of drainage and percolation here, I'm using them in somewhat the same sense: A soil mix that drains down 'fast' should also percolate 'up' fast (hopefully in all directions with good wetting ability). I feed my young sprouts and seedlings from the bottom so percolation is important to me, especially during the first month or two. Later on and after the seedlings are moved outside and I begin drench liquid feeding from the top, drainage plays a major roll.
I think composted forestry products are a great addition to media mixes if you're going to grow your seedlings all the way to (n + 4) or ( n+ 5), etc. That's more or less, pot culture. I grow my seedlings only through (n + 1), then set them out in the garden, so, I never really would get to take full advantage of the slow release of nutrients long term as you do, Rick. They do make the soil mix light and airy.
One note about the soil temperature with the microwave. The soil temperatures do actually reach 160'F on the ones I checked. Whether it's foolproof or not, I don't know for sure, but it's a step I take to maximize survival (hopefully). That's my objective all the way through ( n + 1), then mother nature and I will start the selection and culling process.
I admire those who like to parallel mother nature as much as possible with seeding. It's just something I don't do.
