Fellow Cornhusker,
I am also from Nebraska. On Target says you are a little on the stiff side with the 300's, but I think the consensus is to go with the 300's. The 400's will be way too weak and and it is better to be on the stiff side. I haven't seen anyone selling the 340's in the kinetic yet, but i have heard they are coming out. Maybe a fellow Rokslider has some insight and will chime in. If wanted too you could add an inch or two to your arrow to give it a bit more flex or use the Gold tip weights that screw into the back of the insert. This will give you a higher FOC, right now you are just under 11 with a 430 grain arrow at 290 fps. You could also go with the easton brass HIT insert which I know a few guys on here have done. I think there is a thread talking about it. Let me know if you want to change it up, I can plug it in for you.
Ryan