Using 70% shade cloth would be best for most of the year. If you have to over winter anything, a poly covering can add and removed in the spring. Google 'free plant' which a site run by landscaper/propagator/nurseryman in northern Ohio, z6.

Thanks petzold,I have Mike's book,it's great. That's what
got me started on this idea.I just needed to go a little
bigger than his fish tank idea. Are you saying just shade cloth, no ploy

HAVING LIVED IN THE METRO DETROIT AREA FOR 60 YEARS, I'M VERY AWARE OF THE WINTER CONDITIONS, SO USING THE POLY AS A COVER OVER THE CLOTH ALLOWS YOU MORE FLEXIBILITY, TO COVER OR NOT TODAY/NIGHT, THAT'S ALL.

I am wondering if it will be to hot with the ploy this summer.
when I am trying to root some softwood cuttings.

For best rooting, the temp should be between 70 and 85 degrees F so you have to be monitoring the temp under the cloth.