Take your old screens out in the full sun and look at the amount of shadow they cast, you will probably find that 2 or three is plenty. Please also don't forget that wind is as important in hardening off as is the amount of sun.

Steve

I always start my plants on my screened in porch (roof is screen also) - it seems to be a perfect way to get them used to the elements. it offers some protection from the wind and the sun is filtered. 3-4 hours the first day has never been a problem.

So yes - they should be a big help.

Thanks guys! I layerd two sunside on a covered porch (roof only) they got about 3 hours of filterd sun and then some shade, they still look good. I also considered the wind and they got a nice breeze the whole time. I can really tell wich ones were closer to the fan. So far so good