begreen: absolutely agree. I tried that years back and the air flow created an almost Venturi-like effect and blew wood smoke at me. Good way to learn I guess.
mc: My switch to the b-body is the result of a long arduous and tormenting warrantee claim with PE. As rediculous as it sounds I'm now in a 2nd claim for a third unit. Those details may be better suited to a new thread. Moderator?
saydinli: I would agree with you that it is unlikely to occur, but the edge of the grill opening at either side aligns closely to the side edges of the metal bottom and is adjacent to my wood floor. Unlikely to get in, but if it did so, at the furthest right/left corners of the grill opening, it would be 50/50 as to weather it not it made contact with the wood floor. I noticed on your arch model it may not be as big of a concern as with the non-arch. Your grill louvres are pitched away from the opening. My non arch has flat bars with more direct openings.
BTW the bottom air chamber is far from sealed. It's simply cut to fit sheet metal. Certainly additional CFMs would be drawn through the loose fitting assembly. Your 4" duct may work just fine if things were welded up down there. Not complaining though, as the unit does breath like a dragon as the claims go. Just stating the facts. I've been up and down both a and b bodies with minions and fine toothed combs.
I took a closer look at the non arch and I see what you mean about the grille louvres. Mine a pitched out and downward, so nothing can fall into the opening as easy.Also the louvres don't extend all the way to the very end of the grille.
One easy solution I might consider for a bit of insurance is to install a fine mesh black metal screen in behind the louvres to prevent any embers from accidentally falling in.
By the way what issues are your claims with PE regarding?