NO, you cannot. Well, you can. It is your place, but should it burn down, your insurance company will enjoy not paying the claim. You need an R value of .8 total on your hearth. 1/2" wonder board is .39, so a double thickness and the steel cap will get it for you. Actually, the appliance manuf should be calling out the R value for the hearth. Check your manual.
I'm installing a woodstove in the house and am going to make my hearth as listed above. One inch of wonder board and the cap will be 1/4" plate. I'm going with the plate to avoid having to repair the hearth. If I do it with tile or some thin slate or stone if history is any guide, I will break it. When I need to make fat piece of wood thinner and it is next to the stove I will split it there and not have to worry about breaking the plate. I'll clean it and repaint every spring if necessary, but paint is easier than tile. I am also fabricating a lower heat shield for my Vermont Castings Encore stove.
During the houses re-model I tore down the old stone fireplace. It had a fire brick hearth on top of concrete. I was shocked t see how charred the wood framing below the fireplace was. Was it only one fire or 100 from igniting. With Pyralysis the more you heat wood the lower its kindling temperature becomes. You create charcoal and one day it goes off.
I am installing a wood stove In my work shop, which has a wood floor in it. My question is, would a sheet of 1/4in. thick deck plate by itself be ok to set stove on it? Plate is 4'x5'.