@jackiboi_11 --
The IRIS is a very stable rocket due to the size of the four fins and mine flew VERY well on an RMS 54/1706 K550W and K1100T motors.
But my 4-inch IRIS was pretty heavy so do be sure you've got enough thrust to get your IRIS moving by the time it reaches the end of your rail.
Opinions vary but IMO, the rail guides should be low on the airframe to give you as much rail as possible before the rocket transitions to free flight.
And if you think about the definition of the Barrowman Center of Pressure, it is the axial location where the net normal force acts on the rocket when the angle of attack is a low angle.
For that reason, I like to place one rail guide at -or- just above the CP and one below it to minimize the torque on the rail buttons when the rocket is sitting on the rail in the wind.
It sounds like what you've got ?
If this is your level 1 rocket then be sure to choose an H or an I motor that gets your IRIS going off the rail ( H550ST or an I500T look like good DMS candidate motors ) ...
my $0.02 ... HTH
-- kjh