I don't shoot my Avenger much at this point mainly because it is so long. It shoots pretty well but could be better, I suspect, with more work. The shroud mount is plastic. A metal bushing would be better, I think. There is one bushing spacing the shroud out from the barrel about mid-way. I have and recommend an in shroud moderator. With holes in the back of the shroud my noise level is about 85db and I avoided making the gun any longer than it already was. It also positions the front of the barrel.
If I was going to mess with it some more, and I may some day, I would try different barrel to shroud spacers, preferable with O-rings for shroud and barrel contact. If I could find a metal rear shroud mount I'd get that too. Right now you have a barrel supported by a grub screw at the back and a little unimpressive plastic piece in the shroud. Supporting the barrel better with the shroud seems like it would help eliminate fliers. But where they should be located along the barrel length would need to be determined by testing.
I've been mainly shooting my P35s which are lighter and less than 30 inches long. They're bullpups. At the front of their barrel they have a cast aluminum piece screwed onto the barrel and contacting the shroud with an O-ring. The action clamps to the barrel at two points along it's length. The barrel is thus much better supported. My older 25 caliber shoots worse than my 25 Avenger. But my newer 177 and 22 caliber P35s shoot better than my Avenger. I don't think the accuracy difference is all in the barrel support and possibly not at all in the barrel support. But I hunt with my guns and the P35 arrangement seems much more solid for hunting. I think the Avenger is pretty light even for target shooting.