Seed starting question

I do a soak and into the dirt. works well for me. KISS

Glass of water for 24 hrs then into a coco plug I inoculate the seed with mycorrhizal when soaked..

I'd stick to the same composition of medium for the seedlings. This way the plug doesn't absorb more or less water than what is around it when you pot up. If it is heavily amended, have a small batch that is only lightly amended or not at all if it's the same drainage/aeration characteristics. You can make other options work, but the consistency of how it dries and handles water is probably more important. ---- coco-based? So it's amended like a soil or is it inert.. if amended like a soil, treat it like a soil. If it is "soilless" treat it as soilless. Coco itself does not really change anything. It holds less water per volume, so you need less perlite or similar for proper aeration and drainage characteristics, but even that equals out with proper ratio.. coco is no diffrent in this respect, either. you shoot for the same target gas:water mixture. It's a myth that it needs moer Ca. that is only true if it is buffered poorly and that will only be a temporary issue as it reaches equilibrium with your fertilizer concentrations. coco doesn't magically need more calcium. It only leaches it off if it is poorly buffered and processed, which can also kill plants in an extreme case. coco absorbs and holds water... it's not magic. coco is a fine choice, but it doesn't require behaviours of the greater context -- soil or soilless in this case. Recognize the risk of Na+ sickness and out of balanced buffering... if you see a batch is making seedlings sick, could be the coco.