Frank, no...haven't used the baggie method for conifers or for anything else for that matter, but had you thought about reducing your mortality rate by sowing in a regular potting medium where they don't require transplanting quite so quickly?

I see you are a zone 8 also; I sow conifer seeds in good quality potting soil in 5" minimum deep pots, top with grit or fine aquarium gravel, place outdoors in winter to germinate as the temps gradually begin to warm. The seedlings are stronger more quickly with natural light and the pot depth allows you to grow them on for several weeks before potting up individually.

Nutritional needs are met, and here where it stays damp into Spring I don't need to pay close attention to watering seed pots. I do find it necessary to put a length of chicken wire over seed pots to keep the sparrows out until germination occurs.