I installed my hampton HI300 over the weekend and need about 9 inches more of an extension. If i am interpreting the manual correctly because the stove is over 3.5 inches high, i dont need anything with any specific R value, just something that will prevent sparks. I would like to build something that is removable but will not damage the hardwood floors underneath as we would like to remove it during the summer months. I was thinking of making a box out of oak trim and laying a few rows of bricks or tiles, but how would i protect my floor underneath? I dont like the idea of the mat as i have a lab that would think its a great chew toy to run around the house with. Anyone have any other neat suggestions? Picture below.