I've got a lot of experience with the Courier in combat and some experience in the FAS too. I love both ships.
I'm not shocked if this is the result you get without much iCourier experience. It's a different kind of agile to most ships.
A lot of people see agility as pitch speed, and with some good vertical/lateral thrusting thrown in. The courier certainly doesn't have the strongest pitching, but it's got some decent lateral/vertical thrusting. The main advantage I get from the Courier however is how much less momentum it seems to carry than other ships. When you ask it to change direction,
it changes direction. It also gets some respectable speed. What it makes is a very good FA OFF ship-movements are precise and it adjusts well to quick changes. I've had excellent success using this to sit on the inside of ships that are trying to turn in to it, and then strafe past them while hitting their power plant.
What this ship needs to avoid is jousting matches, where it gets vapourised 100% of the time. It lacks serious firepower and yes the shields are great for its size-but they're by no means invulnerable, and recharge very poorly (hence my use of bi-weaves, which suit the iCourier perfectly).
For all the talk of the iCourier's shield strength, its real forte - for me - has been FA OFF flying and crawling around enemies. It dispatches an anaconda far more easily than it dispatches a vulture, and with a good loadout is a total subsystem wrecker. It also notably requires a clever loadout to save weight while adding bulk, because if kept light it's much more agile than people think and neatly hits the higher register of speeds (and man...that boost sound...)
The FAS, like its earlier brother the Vulture (come on, we know that's what it is here

), fits the more typical description of agile, and without learning its ins and outs is a more "natural" dogfighter - not to mention completely drowning the iCourier's firepower.