Isn't a poor mans block off plate a piece of sheet metal to hold it. Its cheap. If you just stick the insulation up there, I would think over time it could get loose and dry from heat and fall down. To me a piece of sheet metal is just a little more work, not hardly any money to speak of. I do understand the desire to want to use a stove but if you have been paying for heat via electric or gas whats a few more days.