[SOLVED] Airspeed in Auto Modes Higher than Expected

Hoping for some steer here. I have a Skywalker 1830 fixed wing with Sony QX1 for large area mapping. The aircraft is generally flying well, has had several rounds of Autotune and I’ve done some TECS tuning too. Whilst the imagery is good, it’s typical mapping/task speed is way above what I want, in fact all auto modes seem to be too fast. To confirm, aircraft does have an airspeed sensor (in good clean air, ARSPD_RATIO is 1.90)

Here are some of my parameters:
ARSPD_FBW_MIN: 12m/sec
ARSPD_FBW_MAX: 25m/sec
TRIM_ARSPD_CM: 1350cm/sec
TRIM_THROTTLE: 50% (although I think this is meaningless when using airspeed sensor?)

The speed which it is flying on the mapping grid is around 20m/sec and going up to 25m/sec in turns. Loiter and RTL are also really fast, to the extent that the airframe looks stressed. This really has be stumped, as I have built around 10 planes now and never had this issue before. Log attached, appreciate any advice.

https://www.dropbox.com/s/tjy8vrfgqxl2mkz/2018-07-16%2012-12-39.bin?dl=0

ARSPD_USE was set to zero! Doh!