Jack, et. al;

I also have an Impact with the AXI 5330-F / Jeti 90 setup. Everything your reading in these posts is absolutely correct.
I didn't use a soft mount; simply the CF firewall and rubber gromets - no vibration (prop balanced very carefully).
I opted to use a balsa crutch along with the foam one supplied. Paranoid about a fuse failure I guess.
IMHO, the rudder set up was the most agonizing. I opted to install the fin post in the fuse first, then the previously hinged rudder. So far so good. BUT, make sure you have enough rudder travel BEFORE you glue it all together.
The plane flies like a dream and am looking forward to flying it in competition this year.

Now the bad news, with 2-TP5300's, a battery tray and rudder servo tray that are admittedly over-kill, my plane weighs 11lbs 14 oz. Hope it never gets weighed! But the extra weight does not seem to adversely affect the flight quality no matter what speed the wind is blowing.

Best of luck, Jim