A friend of mine runs a four bladed head on his Trex 450 without any stabilization. He put extra weight in the nose. He said that it offsets the tendency for the heli to try and balloon up in forward flight as he described it. He just test hopped his Trex 600 with a 3 bladed head and said it flew well without a stabilization package but would need the nose weight or a stabilization package. He went with the stabilizer and installed the GU-365 .
I should note that this guy has been flying helis for years and I’m sure that his advanced skill level must come in to play to some extent.